A respiratory mask assembly for delivering breathable gas to a patient includes a frame to support one of at least first and second compliant patient interfaces and a forehead support adjustably mounted to the frame. The forehead support is structured and configured to be moved between a first position for use with the first patient interface and a second position relative to the frame for use with a second patient interface, whereby the forehead support maintains a horizontal offset distance with the first and second patient interfaces which is substantially constant.