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 an 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, the patient interface comprising: a cushion assembly configured to deliver a flow of air to the patient's airways, the cushion assembly including: a nasal chamber pressurisable to a therapeutic pressure of at least 6 cmH2O above ambient air pressure, the nasal chamber configured to, in use, deliver the flow of air to the patient's nasal passageways; an oral chamber pressurisable to a different level than the nasal chamber, the oral chamber configured to, in use, deliver the flow of air to the patient's mouth; at least one inlet port sized and structured to receive the flow of air into at least the nasal chamber ; a seal-forming structure constructed and arranged to form a seal with a region of the patient's face surrounding an entrance to the patient's airways, said seal-forming structure having at least one hole formed therein such that the flow of air is delivered to at least an entrance to the patient's nares; and a partition forming a wall extending between and separating the nasal chamber and the oral chamber, wherein a first surface of the wall is disposed in the nasal chamber and a second surface of the wall that is opposite the first surface is disposed in the oral chamber, wherein a plurality of holes is formed in the wall extending through the first surface and the second surface to, in use, allow the flow of air to flow from the nasal chamber to the oral chamber in a manner that maintains a pressure in the oral chamber at a level lower than a pressure in the nasal chamber to promote nasal breathing. a nasal chamber pressurisable to a therapeutic pressure of at least 6 cmH2O above ambient air pressure, the nasal chamber configured to, in use, deliver the flow of air to the patient's nasal passageways; an oral chamber pressurisable to a different level than the nasal chamber, the oral chamber configured to, in use, deliver the flow of air to the patient's mouth; at least one inlet port sized and structured to receive the flow of air into at least the nasal chamber ; a seal-forming structure constructed and arranged to form a seal with a region of the patient's face surrounding an entrance to the patient's airways, said seal-forming structure having at least one hole formed therein such that the flow of air is delivered to at least an entrance to the patient's nares; and a partition forming a wall extending between and separating the nasal chamber and the oral chamber, wherein a first surface of the wall is disposed in the nasal chamber and a second surface of the wall that is opposite the first surface is disposed in the oral chamber, wherein a plurality of holes is formed in the wall extending through the first surface and the second surface to, in use, allow the flow of air to flow from the nasal chamber to the oral chamber in a manner that maintains a pressure in the oral chamber at a level lower than a pressure in the nasal chamber to promote nasal breathing. <EOS>