PURPOSE: To evaluate the major radiologic features of chronic focal pancreatitis in various imaging studies, with special emphasis on CT and ERCP findings. MATERIALS AND METHODS: From 1991 to 1995, twelve patients were pathologically proved to be suffering from focal chronic pancreatitis after pancreatico-duodenectomy ; for retrospective evaluation, imaging studies were available for eight(seven men, one woman ; mean age 58.9±6.6, range 47 to 67). Clinical, surgical, and radiological findings, including CT(n=8), ultrasound(n=7), ERCP(n=8) andUGI(n=3) were analysed. RESULTS: Seven male patients had suffered from chronic alcoholism for between 20 and 50years. Serum bilirubin levels were normal in eight patients and alkaline phosphatase levels were normal in seven patients. Serum CA 19-9 levels were normal in all five patients who had undergone preoperative evaluation. Seven patients(87.5%) showed focal enlargement without definable margin on CT, and five of the six lesions detectable on ultrasound(83.3%) were ill defined hypoechoic nodules. Dilated side branches within lesions were seen in five ofeight patients(83.3%) on CT and ERCP. Double duct signs were observed in siven(87.5%) patients, and dilated intrahepatic ducts in six(75%), with diameters ranging from 5 to 8mm(average : 5.42±1.96mm). The average ratio ofpancreatic duct caliber to gland width was 0.33±0.19. None of the patients had calcification within the lesionand one case showed intraductal calcification. None showed perivascular fat obliteration around the superiormesenteric artery or celiac axis. The average biductal distance between abnormal common bile duct and theimmediately adjacent pancreatic duct was 4.0±1.15mm. One of three cases who under went a UGI examination showed severe luminal narrowing and mucosal thickening in the second portion of the duodenum, another showed double contour, and the other merely showed widening of the C-loop of the duodenum. CONCLUSION: Chronic focalpancreatitis mostly demonstrated ill defined focal enlargement and double ductal dilatation. Dilated side brancheswithin the lesion, no vascular encasement, a mild degree of intrahepatic ductal dilatation, a ratio of pancreatic duct to parenchymal width of less than 0.5, and clinical findings including chronic alcoholism and normal CA 19-9serum level may be reliable indicators for differentiating chronic focal pancreatitis from pancreatic cancer.