Biliary cystic tumors, such as cystadenoma and cystadenocarcinoma, are rare cystic tumors of liver accounting for fewer than 5% of all intrahepatic cysts of biliary origin. Most biliary cystic tumors arise from intrahepatic bile duct and 10-20% arise from extrahepatic bile duct like common hepatic duct, common bile duct, and gallbladder. The first case report of biliary cystic neoplasm in Korea dated back to 1975 by Bae et al, and over 40 cases of cystadenoma and 35 cases of cystadenocarcinoma were reported since then. These tumors usually present in middle-aged women with a mean age of 50 years. Biliary cystadenomas are lined by single layer of cuboidal or columnar epithelium and are very often multilocular with septal or papillary foldings. Over 80% of cystadenoma have dense mesenchymal stroma composed of dense spindle cells, like ovary. The epithelial lining of cystadenocarcinoma exhibits cellular atypia, mitotic activity, and infiltrative growth, but part of lining epithelium retain the feature of cystadenoma, which support the adenoma-carcinoma sequence. The size of tumors varies from 1.5 to 35 cm. Many patients are asymptomatic, except for the presence of palpable mass. When symptoms are present, they include epigastric or right upper quadrant pain or jaundice by enlarged mass. Biliary cystic tumor should be considered when a single or multilocular cystic lesion with papillary infoldings is detected in the liver by computed tomogram (CT) or ultrasound (US). Cystic wall and internal foldings can be seen enhanced by enhanced CT. US reveals a hypoechoic cystic mass with echogenic septation or papillary infoldings. Cystadenocarcinoma should be suspected when there is elevated mass or nodule in the wall or foldings, or thickened cystic wall on CT or US. But it is extremely difficult to differentiate between cystadenoma and cystadenocarcinoma by imaging alone. Increased tumor markers, carcinoembryonic antigen and carbohydrate antigen 19-9, in serum or cystic fluid have been reported in biliary cystic tumor. But tumor markers cannot distinguish cystadenocarcinoma from cystadenoma or both from other cystic lesions of liver. Malignant cells are not usually recovered in patients with cystadenocarcinoma who underwent cystic fluid cytology before and during surgery. The treatment of choice is radical excision of the mass by means of lobectomy or wide tumor excision. Aspiration, marsupialization, and drainage must be avoided. Inadequate excision of both cystadenoma and cystadenocarcinoma may lead to recurrence. Prognosis after complete excision is excellent.