A patient interface for delivery of a supply of pressurised air or breathable gas to an entrance of a patient's airways comprising: a cushion member that includes a retaining structure and a seal-forming structure permanently connected to the retaining structure, the seal-forming structure comprising a pair of nasal pillows constructed and arranged to provide a substantially sealed path for the breathable gas to the nares of the patient, and to form a seal at least in part on a columella region of the patient's nose; and a frame member, wherein the retaining structure and the frame member are repeatedly engageable with and disengageable from one another, wherein a gas chamber is formed at least in part by engagement of the cushion member and the frame member, wherein the cushion member comprises a sealing lip that is a continuous inner peripheral edge integral to the seal-forming structure and that seals against the frame member by interference from the sealing lip deflecting against the frame member to create a sealing force when the retaining structure and frame member are attached to one another, wherein the sealing lip extends inwardly around a perimeter of a junction between the cushion member and the frame member in an undeformed state such that the sealing lip is deflected toward the seal-forming structure by engagement with the frame member when the cushion member and the frame member are attached, wherein the sealing lip is arranged to be urged against the frame member with greater force by an increase in air pressure within the cushion member to cause the sealing force between the seal-forming structure and the frame member to increase. a cushion member that includes a retaining structure and a seal-forming structure permanently connected to the retaining structure, the seal-forming structure comprising a pair of nasal pillows constructed and arranged to provide a substantially sealed path for the breathable gas to the nares of the patient, and to form a seal at least in part on a columella region of the patient's nose; and a frame member, wherein the retaining structure and the frame member are repeatedly engageable with and disengageable from one another, wherein a gas chamber is formed at least in part by engagement of the cushion member and the frame member, wherein the cushion member comprises a sealing lip that is a continuous inner peripheral edge integral to the seal-forming structure and that seals against the frame member by interference from the sealing lip deflecting against the frame member to create a sealing force when the retaining structure and frame member are attached to one another, wherein the sealing lip extends inwardly around a perimeter of a junction between the cushion member and the frame member in an undeformed state such that the sealing lip is deflected toward the seal-forming structure by engagement with the frame member when the cushion member and the frame member are attached, wherein the sealing lip is arranged to be urged against the frame member with greater force by an increase in air pressure within the cushion member to cause the sealing force between the seal-forming structure and the frame member to increase.