Background. Cephalometry is useful as a screening test for anatomical abnormalities in patients with obstructive sleep apnoea syndrome (OSAS). Objective. To evaluate comprehensively the cephalo metric features of children with OSAS, with or without adenotonsillar hypertrophy, and to elucidate the relationship between cephalometric variables and apnoea-hypopnoea index (AHI) severity. Materials and methods. The study population consisted of 39 children, aged 4-12 years, with OSAS. Cephalometry was analysed using 11 measurements of the bony structures, their relationships and the size of the airways. Additionally, adenoid and tonsillar hypertrophy were graded. Results. Cranial base angles (BaSN and BaSPNS) were found to correlate with increasing levels of AHI scores (P<0.001). Protrusion of the maxilla (SNA) and mandible (SNB) did not correlate with AHI scores (P>0.05). The length of the mandibular plane (GnGo) and the minimal posterior airway space (MPAS) were inversely correlated with AHI scores (P<0.001). There was positive correlation between MPAS and GnGo (r=0.740, P<0.001), and negative correlation between MPAS and gonial angle (ArGoGn) (r=-0.541, P<0.001). There was significant correlation between cephalometric data and adenotonsillar hypertrophy concerning BaSN, BaSPNS, ArGoGn, GnGoH, BaN-GnGo, MPAS, GnGO and MPH (P<0.001). Conclusions. There is significant correlation between cephalometric data and AHI score severity in children with OSAS. Adenotonsillar hypertrophy affects the cephalometric measurements adversely. The study clearly mandates the institution of early and effective therapy of adenotonsillar hypertrophy in children with OSAS.