An elastomeric cushion for a breathing mask is configured for sealed delivery of a flow of breathable gas at a positive pressure with respect to ambient air pressure to an entrance of a patient's airways including at least an entrance of the patient's nares. The elastomeric cushion includes a sealing lip with an elastomeric wall configured to form a seal with the patient's face. An elastomeric wall thickness of the sealing lip is varied so that when the sealing lip sealingly engages the patient's face, a portion of the seal at the patient's nose bridge is formed by a relatively thin-walled portion of the sealing lip and other portions of the seal are formed by relatively thick portions of the sealing lip.
