A patient interface for sealed delivery of a flow of air at a continuously positive pressure with respect to ambient air pressure to an entrance to a patient's airways including at least entrance of a patient's nares, wherein the patient interface is configured to maintain a therapy pressure in a range of about 4 cmH2O to about 30 cmH2O above ambient air pressure in use, throughout a patient's respiratory cycle, while the patient is sleeping, to ameliorate sleep disordered breathing; said patient interface comprising: a cushion assembly including: a plenum chamber at least partially forming a cavity pressurisable to a therapeutic pressure of at least 6 cmH 2 O above ambient air pressure, said plenum chamber including a plenum chamber inlet port sized and structured to receive a flow of air at the therapeutic pressure for breathing by a patient; and a seal-forming structure having a sealing portion constructed and arranged to form a pressure-assisted seal with a region of the patient's face surrounding an entrance to the patient's airways inferior to a nasal bridge region of the patient's face, said sealing portion having a hole formed therein such that the flow of air at said therapeutic pressure is delivered to at least an entrance to the patient's nares, the seal-forming structure constructed and arranged to maintain said therapeutic pressure in the cavity throughout the patient's respiratory cycle in use, wherein the seal-forming structure includes a flexible support structure to support the sealing portion, the sealing portion being configured to seal with an underside of the patient's nose including the patient's subnasale and the patient's pronasale, wherein the seal-forming structure includes a seal biasing portion disposed with the sealing portion along a posterior patient-facing surface of the cushion assembly, the seal biasing portion including at least one of fold, pleat or undulation extending between the sealing portion and the support structure, wherein the seal biasing portion is configured to inflate upon pressurization of the cavity in use thereby causing the sealing portion to extend or telescope beyond other portions of the posterior patient-facing surface of the cushion assembly in a direction towards at least a portion of the patient's face. a cushion assembly including: a plenum chamber at least partially forming a cavity pressurisable to a therapeutic pressure of at least 6 cmH 2 O above ambient air pressure, said plenum chamber including a plenum chamber inlet port sized and structured to receive a flow of air at the therapeutic pressure for breathing by a patient; and a seal-forming structure having a sealing portion constructed and arranged to form a pressure-assisted seal with a region of the patient's face surrounding an entrance to the patient's airways inferior to a nasal bridge region of the patient's face, said sealing portion having a hole formed therein such that the flow of air at said therapeutic pressure is delivered to at least an entrance to the patient's nares, the seal-forming structure constructed and arranged to maintain said therapeutic pressure in the cavity throughout the patient's respiratory cycle in use, a plenum chamber at least partially forming a cavity pressurisable to a therapeutic pressure of at least 6 cmH 2 O above ambient air pressure, said plenum chamber including a plenum chamber inlet port sized and structured to receive a flow of air at the therapeutic pressure for breathing by a patient; and a seal-forming structure having a sealing portion constructed and arranged to form a pressure-assisted seal with a region of the patient's face surrounding an entrance to the patient's airways inferior to a nasal bridge region of the patient's face, said sealing portion having a hole formed therein such that the flow of air at said therapeutic pressure is delivered to at least an entrance to the patient's nares, the seal-forming structure constructed and arranged to maintain said therapeutic pressure in the cavity throughout the patient's respiratory cycle in use, wherein the seal-forming structure includes a flexible support structure to support the sealing portion, the sealing portion being configured to seal with an underside of the patient's nose including the patient's subnasale and the patient's pronasale, wherein the seal-forming structure includes a seal biasing portion disposed with the sealing portion along a posterior patient-facing surface of the cushion assembly, the seal biasing portion including at least one of fold, pleat or undulation extending between the sealing portion and the support structure, wherein the seal biasing portion is configured to inflate upon pressurization of the cavity in use thereby causing the sealing portion to extend or telescope beyond other portions of the posterior patient-facing surface of the cushion assembly in a direction towards at least a portion of the patient's face.