Introduction:Obstructive sleep apnea syndrome (OSAS) is characterized by episodes of upper respiratory tract obstruction, decreased oxygen saturation, and sleep fragmentation during sleep, as well as excessive daytime somnolence. Cephalometric analysis offers distance, angle, area, and volume measurements between separate reference points belonging to bony and soft tissues on a film. Cephalometric measurements made with multislice computed tomography (CT) are quite helpful for standardization of measurements and obtaining highly reliable results. The aim of the current study was to make cephalometric measurements with multislice CT in OSAS patients and compare their results with those of a healthy control population. The authors also aimed to determine, which cephalometric parameters might be more valuable for diagnosis of OSAS.Materials and Method:This study included 30 patients who were diagnosed with severe OSAS (apnea-hypopnea index >30) by an overnight polysomnography study, performed for suspected OSAS and 10 healthy controls without snoring or apnea who underwent three-dimensional head & neck multislice CT for any indication. All patients underwent a three-dimensional head & neck multislice CT to make cephalometric measurements and compare them across the groups.Results:ANS-PNS (anterior and posterior nasal spine), Go-Gn, and UP-PhW distances, as well as sella-nasion-A and sella-nasion-B angles, were significantly lower in the OSAS group compared with the controls (P<0.05). Mandibulas plane -H, UD, TT-EA, ANS-B, PNS-TB, TT-TB, B-N, and PNS-PhW distances were significantly higher in the patient group compared with the controls (P<0.05).Conclusions:Our study reached the conclusion that some cephalometric measurements showed significant differences in patients with obstructive sleep apnea compared with the control group, and hence may lead to a susceptibility to having OSAS. Cephalometric measurements performed with multislice CT have come to the forefront as one of the most important tools for diagnosis of OSAS. An inferiorly located hyoid bone may be most commonly responsible for apnea episodes. It was also concluded that an inferiorly located hyoid bone might have been the result of maxillomandibular underdevelopment.