A cushion (10) for a patient interface that delivers breathable gas to a patient includes a base wall (28) structured to be connected to a frame, an underlying support cushion (30) extending away from the base wall (28) towards the patient's face in use, and a membrane (32) provided to substantially cover at least a portion of the underlying cushion (30). The membrane (32) is adapted to form a continuous seal on the patient's face. The underlying cushion (30) has a spring-like connection with the base wall (28). The underlying cushion (30) and/or base wall (28) define a spring constant that varies along a length of the seal.