Biliary cyst are rare with predominating occurrence in females of the Asian population. More than 60 % bile duct cysts are diagnosed in the first decade of life; about 20 % go undiagnosed into adulthood. The cause of biliary cyst has been disputed. Based on clinical and experimental data, genetic (congenital malformation theory) and acquired factors (long common channel theory) may be involved. Biliary cysts are classified according to the site, extent and shape of cystic anomaly. Most complete and practical classification recognizes five types of bile duct cysts. Clinical presentation is a little different in children and adults. The most frequent symptoms are intermittent icterus, abdominal pain and cholangitis, in children palpable mass in abdomen. Basic for diagnosis are clinical symptoms and imaging methods (MRCP and ERCP). The most serious complication is cholangiocarcinoma, which represents a 20-to 30-fold risk in patients with biliary cyst compared to the general population. Biliary cyst treatment is surgical with complete primary cyst excision with Roux-en-Y hepaticojejunostomy reconstruction and cholecystectomy. For Caroli´s disease sometime liver transplantation may be an _option. The complete cyst resection and cholecystectomy is the best prevention for arise of carcinoma.