The Authors report on a rare congenital anomaly of the biliary tract characterized by an accessory choledochus, which drained the inferior paramedian segments of the liver. Such anomalous duct emerged from the hepatic hilum right behind the cystic artery, the cystic duct and the gallbladder to join the primary choledochus few millimeters from the papilla of Vater. At the point of junction, in the posterior aspect of the II duodenal portion, a choledochal diverticulum containing cholesterin and bilirubin stones was also present. Surgery was indicated by the onset of a pseudo-obstructive syndrome followed by jaundice. At laparotomy the exact diagnosis was possible. The intervention consisted in a choledochotomy and duodenotomy with tube drainage and exeresis of the choledochal cyst containing the stones.