The present invention relates to a patient interface (451) for delivering pressurized breathable gas to a patient, the patient interface comprising: a sealing portion (450) adapted to form a seal with the patient's face, the sealing portion comprising: an opening (455) adapted to receive the pressurized breathable gas； an outer sealing margin (534) configured to seal with the patient's face； and a transition region (536) between the opening and the outer sealing margin that gradually increases in size from the opening to the outer sealing margin.
