Three male patients aged between 50 and 70 years were referred with jaundice and weight loss. Imaging showed a pancreatic mass and changes in the calibre of the choledochal or pancreatic duct, suggestive of malignancy. Two patients were operated on. One patient was considered to have an unresectable carcinoma but showed remarkable clinical improvement after steroids were given for his poor condition. In the other patient a resection was performed. Histology showed IgG4-positive plasma cell infiltration without signs of malignancy. Eventually these patients were diagnosed with auto-immune pancreatitis (AIP). In the third patient AIP was considered beforehand and this patient was treated with steroids. He responded quickly both clinically and radiologically. CT imaging showed complete remission of the mass. AIP is a benign inflammatory process which can mimic pancreatic carcinoma. In doubtful cases, a short trial of steroids might be considered.