To ascertain whether there are structural and functional changes in the upper airway of obstructive sleep apnea syndrome (OSAS) pts. We studied 33 pts of OSAS with positive polysomnographic tests, 14 pts of non-apnea snore with negative polysomnographic tests, and 18 normal subject by using CT scanner (Somatom Dr 3). The results are as followings 1. There were narrowing region in the upper airway in OSAS pts and the non-apnea snore pts. Most of the narrowings were located at the level of oropharynx, which was correspondent to the level of the soft palate and the uvula. The length of the soft palate and the pre-spinal soft tissue thickness of two groups of pts were larger than non-snore individual. 2. The pharyngeal compliance was significantly higher in OSAS pts than in non-apnea snore pts. 3. There was no localised deposition of fat tissue surrounding the lumen of upper airway. 4. CT scanning is the non-invasive and more useful procedure for the diagnosis of OSAS and also would help to select the pts for surgery.