BACKGROUND: Although obstructive sleep apnea (OSA) is a common disorder, it often goes undiagnosed due to limited availability of the polysomnography (PSG) and a lack of interest in this condition. The aim of this study was to investigate the relationship between severities of obstructive sleep apnea, sleep questionnaires, oropharyngeal findings and cephalometric parameters in patients whom snore. METHODS: Fifty-seven (46 males) patients presenting snoring or other symptoms of OSA were evaluated retrospectively at the sleep disorder clinic in Keimyung University, Dongsan Medical Center were included in this study. All patients completed an overnight polysomnography, several sleep questionnaires and oropharyngic and cephalometric examinations. The sleep questionnaires included the Stanford Sleepiness Scale (SSS), Epworth Sleepiness Scale (ESS), Pittsburgh Sleep Quality Index (PSQI), and Beck Depression Inventory (BDI). The oropharyngeal examinations included tonsil grade and modified Mallampati grade. RESULTS: There were altogether 42 (38 male) patients diagnosed with OSA. The mean age of the patients was 42.4 +/- 12.8 years, the body mass index (BMI) was 26.1 +/- 2.7 kg/m2 and the apnea-hypopnea index (AHI) was 28.1 3 +/- 0.3. Sex difference (male), BMI, tonsil grade and some parameters of the cephalometric examination had a significant positive correlation with the AHI. However, the AHI correlated poorly with the sleep questionnaires. CONCLUSIONS: Although tonsil grade, modified Mallampati grade and some parameters of the cephalometric examination can be utilized as a useful method to evaluate OSA, the AHI correlated poorly with self-reported sleep questionnaires. These findings suggest that the severity of sleep apnea should be quantified with both physiologic and subjective measures.