PURPOSE: To demonstrate a CT technique by which carcinoma of the ampulla of Vater can be more accurately diagnosed, and to describe the radiologic findings this carcinoma. MATERIALS AND METHODS: We retrospectively reviewed CT findings in 26 patients with pathologically proven carcinoma of the ampulla of Vater. One additional cup of diluted oral contrast medium was ingested immediately before the scan. We analysed the difference in detection rate of the mass in the duodenal lumen with and without duodenal luminal opacification of gastrografin.We also evaluated the size and shape of the mass, dilatation of CBD and the pancreatic duct, and lymph node metastasis. In addition, we analyzed multimodality imaging findings ultrasonogram (US) : 13; hypotonic duodenogram (HTDG): 7; ERCP : 17) of carcinoma of the ampulla of Vater. RESULTS: Nodular soft tissue masses protruding into the duodenal lumen were identified in 21 of 26 cases. In 95% of cases (21/22) with favorable opacification and distension of the duodenum, masses were clearly identified on CT imaging. However, in four caseswith poor opacification and distension of the duodenum, masses could not be observed(P=0.000). The mass on CT scanshowed a well-defined margin, round or lobulated contour, and contrast enhancement similar to that of thepancreas. CBD dilatation was identified in 20 cases and pancreatic duct dilatation in 12. On US, protruding massesin the distal CBD were observed in nine of 13 cases(60%) and on HTDG, in six of seven cases(86%). as well-definedfilling defects. Conclusion : Since the accuracy of CT diagnosis of intestinal lesions is directly proportional tothe degree of intestinal distension and opacification with oral contrast, we believe that adequate ct techniquefor distending and opacitying the duodeual lumen are necessary for early diagnosis of carcinoma of the ampulla ofVater.