Abstract: A nasal CPAP treatment apparatus is disclosed with a flow generator coupled to a nasal mask. The mask has a nasal cushion forming a nose-receiving cavity. The cushion has a triangularly-shaped frame of resilient material with a mask engaging portion connected by a side wall to a face engaging portion which has a nasal bridge region, a cheek region and a lip region. The cushion may have a portion of the side wall in the nasal bridge region being other than straight to provide an improved sealing in the nasal bridge region. A plurality of membranes, preferably three, of resilient material extend substantially around the triangularly-shaped frame. Some of the membranes are thicker in the lip region than in the nasal bridge region to improve fit of the cushion in use.