We report a 74-year-old Japanese woman with a spontaneously vanishing pseudocyst in the remnant pancreas after pylorus-preserving pancreatoduodenectomy for intraductal papillary-mucinous adenoma of the pancreas. A cystic lesion appeared in the remnant pancreas 6 months after the operation and had disappeared 3 months later. When a cystic lesion is encountered in the remnant pancreas after pancreatectomy for mucin-hypersecreting tumor of the pancreas, pseudocyst, as well as recurrence, should be considered in the differential diagnosis. Additional resection would likely cause considerable morbidity, with loss of endocrine and exocrine functions.