Three cases of papillary cystic neoplasm of pancreas were experienced in young females(20,26 and 23 years old respectively). Chief complaints were only mass and intermittent pain on epigastrium. All laboratory data were insignificant except huge masses on the epigastrium. Well circumscribed masses were noted in body(1 case) and tail (2 cases), measuring 20, 12 and 16 cm in diameters respectively, which were simply excised, radically resected and distal pancreatectomized. Cut surfaces showed thick fibrous capsules containing solid mass with partially cystic areas filled by hemorrhage and necrosis. Evidence of metastasis was not noted in all cases. Microscopically, they showed typical patterns of papillary cystic tumor described by others. Ultrastructurally, tumor cells showed two different tones of cytoplasm; dark and light. They showed indented nuclei, abundant mitochondriae, but zymogen granules and neurosecretory granules were not noted. These findings suggested that the tumor was originated from small ducts associated with intercalated duct. All patients are in good conditions for 14, 16 and 12 months after surgery respectively.