Currently, there is no information available regarding craniofacial morphology of Croatian patients with obstructive sleep apnea (OSA). The aim of the study was to determine the craniofacial characteristics of patients with OSA and to assess the association of cephalometric and anthropometric variables related to craniofacial morphology with the apnea hypopnea index (AHI). Anthropometric measurements and upright lateral cephalometric radiographs were obtained from 20 male patients with OSA and 20 male controls. The 20 OSA patients were classified into two groups on the basis of body mass index (BMI) as obese and non-obese. Twenty three variables were identified and calculated for each cephalometric radiograph. OSA was defined as AHI > or = 5/hour. The OSA patients showed greater body mass index (BMI), neck circumference (NC) and cranial index (CI) and lower facial index (FI) compared to the controls (p < 0.01). The patients with OSA showed significant cephalometric features as opposed to the controls: smaller linear distance between gonion and menton and anterior cranial base, greater linear distance from the hyoid bone to the mandibular plane, and from the posterior nasal spine to the tip of the soft palate. Furthermore, they showed reduced upper airway width at two levels: the nasopharynx, and the region of posterior airway space, smaller linear distance from the hyoid bone to the posterior wall of the nasopharynx and greater upper airway length. They also displayed significantly increased craniocervical angulation, larger angle between supramentale, menton and hyoid bone and larger angle between posterior nasal spine, supramentale and hyoid bone. The obese OSA patients showed greater neck circumference (NC) compared with the non-obese OSA. The obese OSA patients showed significant cephalometric features compared with the non-obese OSA patients: larger craniocervical angles larger angle between the third cervical vertebra, the centre of sella turcica and the posterior nasal spine, furthermore, greater linear distance between the hyoid bone and the third cervical vertebra and smaller linear distance from the hyoid bone to the posterior wall of the nasopharynx. In our study, AHI was significantly correlated with cephalometric measurements S-Go, S-H, H-C3 and S-PNS-C3.