The ComboEditorTool is a derived xamComboEditor. Like the other editors, the xamComboEditor has a render template (i.e. the default template) and an edit template (the ControlTemplate used while in edit mode). When not in edit mode (i.e. the default state), the control's default template includes elements like a toggle button etc. to look like it will while it is in edit mode. The edit template includes a ComboBox whose style is bound to the ComboBoxStyle property. So setting the ComboBoxStyle is just going to affect the look of the ComboBox hosted within the edit template (i.e. within the control while in edit mode). You can either create a custom template for the default/render template using the default xaml we ship with the product (located in the DefaultStyles directory). Or you could possibly set the IsAlwaysInEditMode property to true but you still may need to tweak the edit template to work best with your template. Note the default style for the ComboBox used within the edit template binds to properties on the containing XamComboEditor via the attached ComboEditor property (e.g. DropDownButtonStyle, MinDropDownWidth, MaxDropDownWidth, etc.)