The important anatomy of paranasal sinuses is well documented by osteomeatal unit CT scan(OMU CT). But the accuracy and reliability of OMU CT is not absolute. We report comparative degree of the preoperative OMU CT findings with amount of the intraoperative sinus endoscopic surgical findings in 90 patients(148 cases) undergoing therapeutic sinus endoscopic surgery in department during recent two years. 1) Among all the patients(90 patients), correspondance rate was 43.3%(39 patients), discrepancy rate was 56.7%(51 patients). 2) In the discrepancy of OMU CT and intraoperative findings, overestimated cases in frontal sinus, maxillary sinus, anterior ethmoid sinus, posterior ethmoid sinus and sphenoid sinus were 2 cases(4.1%), 5 cases(3.4%), 2 cases(1.4%), 4 cases(3.3%) and 2 cases(4.7%) respectively, and underestimated cases were 5 cases(10.2%), 13 cases(8.8%), 15 cases(10.1%), 10 cases(8.3%) and 4 cases(9.3%) respectively.