Recently endoscope is widely used in operation of chronic sinusitis and various nasal diseases, For the precision of endoscopic sinus surgery, preoperative PNS CT scan is essential. The authors analyzed the findings of PNS CT and endoscopic sinus surgery in 62 patients (120sides) undergoing endoscopic sinus surgery in our hospital from May 1994 to July 1995. The results obtained were as follows ; Among 62 patients(120sides), correspondence rate between preoperative CT findings and operative findings was 89%, 217 of 243 cases, and the cases of total opacification were excluded. We suggest that the extent of surgery should not be determined only be the CT findings, bacause some cases are pathologic in operative findings although CT findings indicate them as negative.