Congenital cystic dilatation of bile ducts is a rare condition. We report a retrospective study about 18 patients having congenital bile duct cysts. According to Todani's classification, 11 cases were type I and 7 were type V. Six patients from the first group had a pancreatobiliary maljunction. A total resection of the cyst was conducted in the type I cysts. Anatomopathologic examination showed an adenocarcinoma of a common bile duct cyst. In one case, a cancer of the gall bladder associated to a common bile duct cyst in another case. Three patients with segmental dilatation of intrahepatic bile ducts (type V) underwent liver resection. Four patients had a diffuse form, one of them was treated by percutaneous drainage, and in the other cases a hepatojejunostomy was performed. Postoperative course was complicated with acute cholangitis in these four cases. Percutaneous drainage and antibiotics allowed a positive outcome in most of the cases. In one case, secondary biliary cirrhosis occurred as a long-term complication. Congenital cystic dilatation of bile ducts is considered to be a precancer state. Enterocystic anastomosis is proscribed and the resection has to be as complete as possible.