Abstract: A head positioning device for use in radio therapy is described for positioning a patient's head. The head positioning device comprises a head plate for supporting a patient's head; a base plate for connection to a mechanical couch; and a head plate adjustment assembly connecting the head plate to the base plate wherein the head plate adjustment assembly is arranged to vary the relative pitch, yaw and roll of the head plate relative to the base plate. The head positioning device is arranged to be attached to a mechanical couch with the head plate and the head plate adjustment assembly cantilevered off the end of the couch and the head plate adjustment assembly suspended beneath the head plate and the base plate.