Obstructive sleep apnoea-hypopnoea syndrome (OSAHS) is a complex disease with a multifactor aetiology. OSAHS is strongly associated with obesity, but there are many other clinical risk factors, such as the dentofacial characteristics of hard and soft tissues, hyoid bone position, neck circumference, upper airway spaces and nasal respiration. A descriptive cross-sectional study was carried out involving 13 patients (one man and 12 women) with severe obesity in order to evaluate specific physical dentofacial characteristics through a cephalometric examination. Cephalometry was analysed using 29 measurements of the hard and soft tissues of the craniofacial structures and dimensions of the upper airways. The demographic data revealed a mean body mass index of 48 ± 6.26 kg m−2 and cervical circumference of 43 ± 3.69 cm. No patient exhibited important facial asymmetry and facial types 1 (normal) and 3 (mandible forward) were the most prevalent. Septal deviation was observed in 46% of patients. The most prevalent modified Mallampati index score was between 3 and 4, while grade 1 was the most prevalent tonsillar hypertrophy index score (46%). Cephalometry revealed angular and linear measurements with normally acceptable values for the hard tissues. Obese patients seem to have a normal craniofacial structure and the risk of developing OSAHS is especially related to obesity.