Abstract: Objective: To study the changes of obstructive levels in oropharynx and rhinopharynx in supine position. Methods: A detailed cephalometric analysis was performed using lateral X-ray films in sitting position and supine position from 15 male volunteers.Results: In the supine position: the soft palate and hyoid bone was displaced posteriorly; the posterior airway space (PAS) got turned more narrow compared to sitting position. Conclusion: Lateral X-ray film in supine position is highly recommended as a valuable tool in the diagnosis, treatment option and prognoses evaluation of obstructive sleep apnea syndrome (OSAS).