Patients with obstructive sleep apnoea syndrome frequently present distinct changes in the craniofacial skeleton that result in a structural narrowing of the pharynx and promote pharyngeal collapse during sleep. The evaluation of the clinical data of patients with and without craniofacial dysmorphia reveals that mean age, mean Broca index and the number of additional diseases is decreased in patients with craniofacial dysmorphia. Young patients or patients with normal weight and OSAS usually present such skeletal changes. The number of sleep-related breathing disorders and the extent of nocturnal desaturation are also decreased in the group of patients with dysmorphia. The structure of sleep is similarly disturbed in both groups. In most cases patients with severe obstructive sleep apnoea have normal cephalometric data.