A full-face mask system for delivery of a supply of gas at positive pressure to a patient for medical treatment includes a shroud, a cushion module adapted to form a seal with the patient's nose and mouth, an elbow, and headgear. The cushion module includes a frame and a cushion. The frame includes an opening that releasably receives a distal end of the elbow with a snap-fit, wherein an inner edge of the opening and the distal end of the elbow together form a retention structure to retain the elbow to the frame.