We presented 3 cases of cystic dilatation of common bile duct classified as type IC, IVB an IVA. All 3 were women, admitted for right upper quadrant pain and jaundice. Two cases proved malignant degeneration in cystic dilatation in first cas and in gallbladder in third. Only the 3rd case had a positive preoperative diagnosis achieved through echography, TPHC, ERPC. Surgical treatment consisted of cysto-jejunal derivation in the cas of the common duct malignant cyst inoperative and cholecystectomy associated with the excision of the dilatation followed by the hepato-jejunal anastomosis in the other 2 cases. Adenocarcinoma of the gallbladder was a pathological surprise. A better knowledge of the risk of cancer on cystic dilations of the common bile duct should lead to an earlier diagnosis of this disease and a preventive treatment by radical excision of the dilatation.