diff --git a/openstack/compute/v2/extensions/bootfromvolume/requests.go b/openstack/compute/v2/extensions/bootfromvolume/requests.go
index 28fef94..9dae14c 100644
--- a/openstack/compute/v2/extensions/bootfromvolume/requests.go
+++ b/openstack/compute/v2/extensions/bootfromvolume/requests.go
@@ -5,40 +5,68 @@
 	"github.com/gophercloud/gophercloud/openstack/compute/v2/servers"
 )
 
-// SourceType represents the type of medium being used to create the volume.
-type SourceType string
+type (
+	// DestinationType represents the type of medium being used as the
+	// destination of the bootable device.
+	DestinationType string
 
-const (
-	// Volume SourceType
-	Volume SourceType = "volume"
-	// Snapshot SourceType
-	Snapshot SourceType = "snapshot"
-	// Image SourceType
-	Image SourceType = "image"
-	// Blank SourceType
-	Blank SourceType = "blank"
+	// SourceType represents the type of medium being used as the source of the
+	// bootable device.
+	SourceType string
 )
 
-// BlockDevice is a structure with options for booting a server instance
-// from a volume. The volume may be created from an image, snapshot, or another
-// volume.
+const (
+	// DestinationLocal DestinationType is for using an ephemeral disk as the
+	// destination.
+	DestinationLocal DestinationType = "local"
+
+	// DestinationVolume DestinationType is for using a volume as the destination.
+	DestinationVolume DestinationType = "volume"
+
+	// SourceBlank SourceType is for a "blank" or empty source.
+	SourceBlank SourceType = "blank"
+
+	// SourceImage SourceType is for using images as the source of a block device.
+	SourceImage SourceType = "image"
+
+	// SourceSnapshot SourceType is for using a volume snapshot as the source of
+	// a block device.
+	SourceSnapshot SourceType = "snapshot"
+
+	// SourceVolume SourceType is for using a volume as the source of block
+	// device.
+	SourceVolume SourceType = "volume"
+)
+
+// BlockDevice is a structure with options for creating block devices in a
+// server. The block device may be created from an image, snapshot, new volume,
+// or existing volume. The destination may be a new volume, existing volume
+// which will be attached to the instance, ephemeral disk, or boot device.
 type BlockDevice struct {
-	// SourceType must be one of: "volume", "snapshot", "image".
+	// SourceType must be one of: "volume", "snapshot", "image", or "blank".
 	SourceType SourceType `json:"source_type" required:"true"`
-	// UUID is the unique identifier for the volume, snapshot, or image (see above)
+
+	// UUID is the unique identifier for the existing volume, snapshot, or
+	// image (see above).
 	UUID string `json:"uuid,omitempty"`
+
 	// BootIndex is the boot index. It defaults to 0.
 	BootIndex int `json:"boot_index"`
+
 	// DeleteOnTermination specifies whether or not to delete the attached volume
 	// when the server is deleted. Defaults to `false`.
 	DeleteOnTermination bool `json:"delete_on_termination"`
+
 	// DestinationType is the type that gets created. Possible values are "volume"
 	// and "local".
-	DestinationType string `json:"destination_type,omitempty"`
+	DestinationType DestinationType `json:"destination_type,omitempty"`
+
 	// GuestFormat specifies the format of the block device.
 	GuestFormat string `json:"guest_format,omitempty"`
-	// VolumeSize is the size of the volume to create (in gigabytes).
-	VolumeSize int `json:"volume_size"`
+
+	// VolumeSize is the size of the volume to create (in gigabytes). This can be
+	// omitted for existing volumes.
+	VolumeSize int `json:"volume_size,omitempty"`
 }
 
 // CreateOptsExt is a structure that extends the server `CreateOpts` structure
diff --git a/openstack/compute/v2/extensions/bootfromvolume/testing/requests_test.go b/openstack/compute/v2/extensions/bootfromvolume/testing/requests_test.go
index 6724dab..7fd3e7d 100644
--- a/openstack/compute/v2/extensions/bootfromvolume/testing/requests_test.go
+++ b/openstack/compute/v2/extensions/bootfromvolume/testing/requests_test.go
@@ -8,7 +8,91 @@
 	th "github.com/gophercloud/gophercloud/testhelper"
 )
 
-func TestCreateOpts(t *testing.T) {
+func TestBootFromNewVolume(t *testing.T) {
+	base := servers.CreateOpts{
+		Name:      "createdserver",
+		FlavorRef: "performance1-1",
+	}
+
+	ext := bootfromvolume.CreateOptsExt{
+		CreateOptsBuilder: base,
+		BlockDevice: []bootfromvolume.BlockDevice{
+			{
+				UUID:                "123456",
+				SourceType:          bootfromvolume.SourceImage,
+				DestinationType:     bootfromvolume.DestinationVolume,
+				VolumeSize:          10,
+				DeleteOnTermination: true,
+			},
+		},
+	}
+
+	expected := `
+    {
+      "server": {
+        "name":"createdserver",
+        "flavorRef":"performance1-1",
+        "imageRef":"",
+        "block_device_mapping_v2":[
+          {
+            "uuid":"123456",
+            "source_type":"image",
+            "destination_type":"volume",
+            "boot_index": 0,
+            "delete_on_termination": true,
+            "volume_size": 10
+          }
+        ]
+      }
+    }
+  `
+	actual, err := ext.ToServerCreateMap()
+	th.AssertNoErr(t, err)
+	th.CheckJSONEquals(t, expected, actual)
+}
+
+func TestBootFromExistingVolume(t *testing.T) {
+	base := servers.CreateOpts{
+		Name:      "createdserver",
+		FlavorRef: "performance1-1",
+	}
+
+	ext := bootfromvolume.CreateOptsExt{
+		CreateOptsBuilder: base,
+		BlockDevice: []bootfromvolume.BlockDevice{
+			{
+				UUID:                "123456",
+				SourceType:          bootfromvolume.SourceVolume,
+				DestinationType:     bootfromvolume.DestinationVolume,
+				DeleteOnTermination: true,
+			},
+		},
+	}
+
+	expected := `
+    {
+      "server": {
+        "name":"createdserver",
+        "flavorRef":"performance1-1",
+        "imageRef":"",
+        "block_device_mapping_v2":[
+          {
+            "uuid":"123456",
+            "source_type":"volume",
+            "destination_type":"volume",
+            "boot_index": 0,
+            "delete_on_termination": true
+          }
+        ]
+      }
+    }
+  `
+	actual, err := ext.ToServerCreateMap()
+	th.AssertNoErr(t, err)
+	th.CheckJSONEquals(t, expected, actual)
+}
+
+func TestBootFromImage(t *testing.T) {
 	base := servers.CreateOpts{
 		Name:      "createdserver",
 		ImageRef:  "asdfasdfasdf",
@@ -19,11 +103,11 @@
 		CreateOptsBuilder: base,
 		BlockDevice: []bootfromvolume.BlockDevice{
 			{
-				UUID:                "123456",
-				SourceType:          bootfromvolume.Image,
-				DestinationType:     "volume",
-				VolumeSize:          10,
-				DeleteOnTermination: false,
+				BootIndex:           0,
+				DeleteOnTermination: true,
+				DestinationType:     bootfromvolume.DestinationLocal,
+				SourceType:          bootfromvolume.SourceImage,
+				UUID:                "asdfasdfasdf",
 			},
 		},
 	}
@@ -36,55 +120,11 @@
         "flavorRef": "performance1-1",
         "block_device_mapping_v2":[
           {
-            "uuid":"123456",
-            "source_type":"image",
-            "destination_type":"volume",
             "boot_index": 0,
-            "delete_on_termination": false,
-            "volume_size": 10
-          }
-        ]
-      }
-    }
-  `
-	actual, err := ext.ToServerCreateMap()
-	th.AssertNoErr(t, err)
-	th.CheckJSONEquals(t, expected, actual)
-}
-
-func TestCreateOptsWithoutImageRef(t *testing.T) {
-	base := servers.CreateOpts{
-		Name:      "createdserver",
-		FlavorRef: "performance1-1",
-	}
-
-	ext := bootfromvolume.CreateOptsExt{
-		CreateOptsBuilder: base,
-		BlockDevice: []bootfromvolume.BlockDevice{
-			{
-				UUID:                "123456",
-				SourceType:          bootfromvolume.Image,
-				DestinationType:     "volume",
-				VolumeSize:          10,
-				DeleteOnTermination: false,
-			},
-		},
-	}
-
-	expected := `
-    {
-      "server": {
-        "name": "createdserver",
-        "imageRef": "",
-        "flavorRef": "performance1-1",
-        "block_device_mapping_v2":[
-          {
-            "uuid":"123456",
+            "delete_on_termination": true,
+            "destination_type":"local",
             "source_type":"image",
-            "destination_type":"volume",
-            "boot_index": 0,
-            "delete_on_termination": false,
-            "volume_size": 10
+            "uuid":"asdfasdfasdf"
           }
         ]
       }
@@ -108,24 +148,24 @@
 			{
 				BootIndex:           0,
 				DeleteOnTermination: true,
-				DestinationType:     "local",
-				SourceType:          bootfromvolume.Image,
-				UUID:                "123456",
+				DestinationType:     bootfromvolume.DestinationLocal,
+				SourceType:          bootfromvolume.SourceImage,
+				UUID:                "asdfasdfasdf",
 			},
 			{
 				BootIndex:           -1,
 				DeleteOnTermination: true,
-				DestinationType:     "local",
+				DestinationType:     bootfromvolume.DestinationLocal,
 				GuestFormat:         "ext4",
-				SourceType:          bootfromvolume.Blank,
+				SourceType:          bootfromvolume.SourceBlank,
 				VolumeSize:          1,
 			},
 			{
 				BootIndex:           -1,
 				DeleteOnTermination: true,
-				DestinationType:     "local",
+				DestinationType:     bootfromvolume.DestinationLocal,
 				GuestFormat:         "ext4",
-				SourceType:          bootfromvolume.Blank,
+				SourceType:          bootfromvolume.SourceBlank,
 				VolumeSize:          1,
 			},
 		},
@@ -143,8 +183,7 @@
             "delete_on_termination": true,
             "destination_type":"local",
             "source_type":"image",
-            "uuid":"123456",
-            "volume_size": 0
+            "uuid":"asdfasdfasdf"
           },
           {
             "boot_index": -1,
@@ -170,3 +209,119 @@
 	th.AssertNoErr(t, err)
 	th.CheckJSONEquals(t, expected, actual)
 }
+
+func TestAttachNewVolume(t *testing.T) {
+	base := servers.CreateOpts{
+		Name:      "createdserver",
+		ImageRef:  "asdfasdfasdf",
+		FlavorRef: "performance1-1",
+	}
+
+	ext := bootfromvolume.CreateOptsExt{
+		CreateOptsBuilder: base,
+		BlockDevice: []bootfromvolume.BlockDevice{
+			{
+				BootIndex:           0,
+				DeleteOnTermination: true,
+				DestinationType:     bootfromvolume.DestinationLocal,
+				SourceType:          bootfromvolume.SourceImage,
+				UUID:                "asdfasdfasdf",
+			},
+			{
+				BootIndex:           1,
+				DeleteOnTermination: true,
+				DestinationType:     bootfromvolume.DestinationVolume,
+				SourceType:          bootfromvolume.SourceBlank,
+				VolumeSize:          1,
+			},
+		},
+	}
+
+	expected := `
+    {
+      "server": {
+        "name": "createdserver",
+        "imageRef": "asdfasdfasdf",
+        "flavorRef": "performance1-1",
+        "block_device_mapping_v2":[
+          {
+            "boot_index": 0,
+            "delete_on_termination": true,
+            "destination_type":"local",
+            "source_type":"image",
+            "uuid":"asdfasdfasdf"
+          },
+          {
+            "boot_index": 1,
+            "delete_on_termination": true,
+            "destination_type":"volume",
+            "source_type":"blank",
+            "volume_size": 1
+          }
+        ]
+      }
+    }
+  `
+	actual, err := ext.ToServerCreateMap()
+	th.AssertNoErr(t, err)
+	th.CheckJSONEquals(t, expected, actual)
+}
+
+func TestAttachExistingVolume(t *testing.T) {
+	base := servers.CreateOpts{
+		Name:      "createdserver",
+		ImageRef:  "asdfasdfasdf",
+		FlavorRef: "performance1-1",
+	}
+
+	ext := bootfromvolume.CreateOptsExt{
+		CreateOptsBuilder: base,
+		BlockDevice: []bootfromvolume.BlockDevice{
+			{
+				BootIndex:           0,
+				DeleteOnTermination: true,
+				DestinationType:     bootfromvolume.DestinationLocal,
+				SourceType:          bootfromvolume.SourceImage,
+				UUID:                "asdfasdfasdf",
+			},
+			{
+				BootIndex:           1,
+				DeleteOnTermination: true,
+				DestinationType:     bootfromvolume.DestinationVolume,
+				SourceType:          bootfromvolume.SourceVolume,
+				UUID:                "123456",
+				VolumeSize:          1,
+			},
+		},
+	}
+
+	expected := `
+    {
+      "server": {
+        "name": "createdserver",
+        "imageRef": "asdfasdfasdf",
+        "flavorRef": "performance1-1",
+        "block_device_mapping_v2":[
+          {
+            "boot_index": 0,
+            "delete_on_termination": true,
+            "destination_type":"local",
+            "source_type":"image",
+            "uuid":"asdfasdfasdf"
+          },
+          {
+            "boot_index": 1,
+            "delete_on_termination": true,
+            "destination_type":"volume",
+            "source_type":"volume",
+            "uuid":"123456",
+            "volume_size": 1
+          }
+        ]
+      }
+    }
+  `
+	actual, err := ext.ToServerCreateMap()
+	th.AssertNoErr(t, err)
+	th.CheckJSONEquals(t, expected, actual)
+}