Aim: This study was aimed to investigate the respiratory variables during wakefulness, otorhinolaryngologic and anthropometric differences, and to clarify their possible associations in patients with obstructive sleep apnea syndrome (OSAS). Method: Apnea-hypopnea index (AHI) was established by overnight polysomnography. Otorhinolaryngologic examination, anthropometric measurements and questionnaire, were performed. Respiratory variables were measured with a cardio-breathing analysis system. Body fat percentages were calculated from the skinfold thicknesses. Result: Among a total of 83 patients, 43 (32 male and 11 female) patients having an AHI score equal or above 10 were diagnosed as OSA, and 40 (27 male and 13 female) patients having an AHI score under 10 were diagnosed as simple snorers. Apnea with witness, flat soft palate, pharyngeal collapse with Muller maneuver, neck antero-posterior and lateral diameters, thorax antero-posterior diameter, and O2 pulse values were found significantly higher in OSAS patients than those in simple snorers. Conclusion: This study suggests that neck antero-posterior and lateral diameters, thorax antero-posterior diameter and O2 pulse might be predicting factors for OSAS. It also emphasizes that pharyngeal collapse with Muller maneuver can be routine diagnostic procedure in evaluating OSAS patients.