A full face mask system for treatment of respiratory disorder with Continuous Positive Airway Pressure equipment suitable to generate a supply of gas at positive pressure to be delivered to a patient's airways, the mask system comprising a frame module; a cushion module provided to the frame module and adapted to form a seal with the patient's face; an elbow module provided to the frame module and adapted to be connected to an air delivery tube to deliver breathable gas to the patient; and headgear removably attachable to the frame module.