A 73-year-old woman was referred to our hospital complainting of swelling of both eyelids and submandibular glands, nausea, and weight loss. She was given a diagnosis of autoimmune pancreatitis because of a marked elevation of serum IgG and IgG4 levels and diffuse swelling of the pancreas with stenosis of the main pancreatic duct. Biopsy obtained from the lachrymal gland revealed aggregated IgG4-positive plasma cells, leading to the diagnosis of Mikulicz's disease. PET-CT revealed an accumulation of FDG in the pancreas, lachrymal glands and submandibular glands, and lymph nodes in the mediastinum, hepatic hilium, bile duct and retroperitoneum. Three months after the initiation of steroid therapy, the serum levels of IgG and IgG4 decreased and FDG accumulations of the systemic lesions were no longer visible on PET.