The localization of the obstruction is crucial in determining the appropriate surgical treatment for obstructive sleep apnea syndrome (OSAS); ApneaGraph has been introduced for diagnosis of OSAS and localization of airway obstruction level. This study aims to evaluate the diagnostic value of ApneaGraph for both clinical staging and site of obstruction. Thirty male OSAS patients were prospectively enrolled in this clinical trial. The following parameter were included to the study: Body mass indexes and neck circumferences of the subjects, Epworth sleepiness scale, site of obstruction detected by flexible endoscopy and ApneaGraph, apnea hypopnea index (AHI), apnea index, hypopnea index, maximal oxygen desaturation and average oxygen saturation which were detected by both polysomnography (PSG) and ApneaGraph devices. Our data presented that, although AHI measured by ApneaGraph and PSG were significantly correlated; severity stages of the subjects were different in 44 % of the subjects when based on AHI of ApneaGraph, compared to PSG. Majority of the changes were from severe OSAS to mild or moderate levels. Similar dominant collapse levels were detected in 64 % of the subjects by both devices. It was seen that transpalatal obstruction was better correlated between ApneaGraph and flexible endoscopy. As a conclusion, we might assume that ApneaGraph can be used as a screener for OSAS and it appears to be a more reliable device to confirm dominancy of palatal level obstruction.