A harness assembly for a nasal mask for communicating breathable gas to a patient's airways, for example, in the administering of CPAP or like breathable gas delivery treatments, includes a cap portion adapted to engage, in use, the occipital region of the skull. The cap portion includes a connector at each end. The harness assembly also includes a pair of upper and lower straps, each of the straps extending between one of the cap connectors and the nasal mask. The harness assembly grips the head in a region substantially fixed relative to the face and, as such, tension of the straps is not substantially affected by head movement.