Nowadays increasing use of abdominal ultrasound in routine check-up may increase the detection rate asymtomatic cystic lesions of pancreas. Even through the majority of the cystic lesions of pancreas is pseudocyst, about 10-15% of those lesions are caused by pancreatic cystic tumor. In the pancreatic cystic tumor, especially, mucinous cystic tumor should be exicised due to its malignant potential, while the pancreatic pseudocyst or serous cystic tumon can be observed for a period or treated medically. Several clinical, radiological, biochemical and pathologic guidelines have been developed in order to distinguish among them. Among pancreatic cystic tumors, mucinous cystic adenocarcinoma is very rare and accounts for only 1% of all pancreatic neoplasms. Unlike extremely poor prognosis of pancreatic adenocarcinoma, mucinous cystic adenocarcinoma has an indolent course and shows a good prognosis after its curative resection. Recently we experienced a 69-year-old woman who had a mucinous cystic adenocarcinoma of the pancreas. We report this case with a review of literature.