A mask system includes a frame (20) adapted to attach headgear, a sealing arrangement (40) releasably connectable to the frame, and an elbow (70) provided to the sealing arrangement and adapted to be connected to an air delivery tube that delivers breathable gas to the patient. The sealing arrangement defines a breathing chamber and is adapted to form a seal with the patient's face. The sealing arrangement includes structure (50) to establish a positive connection with the frame and with the elbow.