The extrapancreatic bile duct lesions in autoimmune pancreatitis are termed sclerosing cholangitis (SC with AIP), which is known to complicate AIP somewhat more frequently than other extrapancreatic lesions. In cases of SC with AIP, differentiation from primary SC, pancreatic cancer, and bile duct cancer is often difficult. In our patient, pancreatic cancer had to be ruled out at admission, given the findings of obstructive jaundice, pancreatic duct stenosis, and swelling of the pancreas. Fluorine-18-fluorodeoxyglucose positron emission tomography was useful in checking for the presence of extrapancreatic lesions, including SC, and was also useful in the evaluation of the response to steroid therapy for following the course of AIP.