Abstract: A respiratory mask assembly is provided. The assembly includes at least one post having a nasal engaging portion on about a first end thereof for delivering treatment gases to the nasal cavity of a patient. A mask having an inlet for receiving treatment gases from a fluid source and at least one receptacle for being sealably engaged with a respective one of the at least one post for delivering treatment gases from the inlet through the receptacle and into the nasal cavity of the patient is provided. The mask is configured for selective sealable engagement with the patient's mouth, patient's nose, or both the patient's mouth and the patient's nose.