OBJECTIVE To explore the value of spiral CT in detecting narrow level of obstructive sleep apnea hypopnea syndrome(OSAHS) through investigating measured parameters of upper airway. METHODS The upper airway levels from the roof of nasopharynx to the inferior border of cricoid cartilage were scanned with spiral CT in 127 OSAHS patients and 52 controls.The coronal and sagittal diameter and the cross sectional areas of palate,uvula,tongue, epiglottis level were measured using image handling workstation.The measured values of each level were divided by the measured values of the cricoid cartilage level,and get relative values.The relative values of the OSAHS patients and controls were compared. RESULTS The relative values of posterior soft palate and uvula region,lingual region and epiglottis regions were statistically different.The difference also existed between genders.The relative values of 46 controls and 17 OSAHS patients were in the normal range. Among 127 OSAHS,the relative values of 110 cases with OSAHS(86.6%) were below the normal range in every region,while in control group,the relative values were found below the normal range in only 6 persons (11.2%).CONCLUSION The relative values of each regions is useful to judge the narrow level of upper airway in OSAHS patients.