The present invention is related to patient interfaces, such as nasal masks (2), particularly though not solely for use in providing continuous positive airway pressure therapy or positive pressure ventilation to patients suffering from obstructive sleep apnoea. In a first form the invention is a patient interface that has securement means (601) releasably attaching the interface to headstraps wherein the securement means (601) is slidably engaged with the patient interface. In a second form of the invention the mask headgear is formed of a plurality of straps (701, 702) where at least one of the plurality of straps is slidably engaged with another of the plurality of straps. In a further form the patient interface may be provided with vertically adjustable engaging means (802) that engage the patient interface with the headgear straps.