Pancreato-biliary maljunctions (PBM) in adults are defined by the presence of an abnormally long common pancreato-biliary duct (more than 15 mm long) formed outside the duodenal wall and/or by high amylase level in the bile. The high amylase level in the bile is the functional expression of a chronic toxic reflux of pancreatic juices into the biliary tree. The presence of the PBM have two basic consequences: (i) formation of congenital cystic dilatations of the bile duct (CCBD) during embryogenesis and (ii) cancerous degeneration of extrahepatic bile ducts including the gall bladder. CCBD are commonly found in Southeast of Asia and in Japan where more than two-thirds of the worldwide cases are reported. Women are more frequently touched. The main manifestations are pain, cholangitis and acute pancreatitis. Cancerous degeneration mainly due to chronic pancreatico-biliary reflux consecutive to the presence of PBM is the most serious complication of CCBD. Its global incidence is about 16% and increases by age and after cysto-digestive derivations widely performed in the past. In 80% of the cases a cholangiocarcinoma involving the extrahepatic portion of the biliary tree including dilated segments such as the gall bladder and/or cystic wall is found. The treatment of choice of most common types of CCBD with PMD is complete excision of most of the sites where cancer may arise and should interrupt the pancreato-biliary reflux. This treatment significantly reduces the incidence of bile duct cancer to 0.7%. However, despite the absence of mortality, the overall morbidity rates reach from 20% to 40%. In the complete excision, the entire common bile duct from porta hepatis to the intrapancreatic portion of the choledochus and the gall bladder are resected. The bile continuity is assured by a hepatico-jejunal Y anastomosis. When there is no CCBD, the high risk of gall bladder cancer in the presence of a PBM justifies by itself a preventive cholecystectomy even if no biliary stone is present.