The diocese may have originally contained Galloway, a suggestion thought to explain the possible attacks of Wimund on Bishop Gilla Aldan of Whithorn.
Richard Oram argues that the creation of the Bishopric of Whithorn probably encouraged the wrath and enmity of Bishop Wimund of the Isles, who seems to have regarded the area as his natural area of authority.
Wimund's bishopric of the Isles had its seat on the Isle of Skye.