Two cases of pancreatitis induced by autoimmunity with PET images using F-18 fluoro-2-deoxy-D-glucose (FDG) are reported. The patients had abdominal pain and were thought to have possible pancreatic neoplasms. In one patient, PET showed intense uptake of the entire pancreas, but a Ga-67 scan yielded a negative result. Because the serum immunoglobulin G level was high, autoimmune pancreatitis was diagnosed in this patient. He underwent steroid therapy and fully recovered. In another patient with positive antinuclear antibodies and hyperglobulinemia, focal intense uptake was found in the head of the pancreas on the FDG PET. She also recovered with steroid therapy. Autoimmune pancreatitis is a relatively new form of chronic pancreatitis and should be kept in mind when making a differential diagnosis of pancreatic cancer with the assistance of FDG PET.