A case of cystic dilation isolated from the cystic duct is described. The patient showed symptoms of chronic calculous cholecystitis; the ultrasonographic examination confirmed the clinical hypothesis and showed a 1.3-cm calculus impacted in the infundibulum of the gallbladder. The hepatic and biliary functions were normal. During surgery, the routine cholangiographic study showed a sizable cyst in the cystic canal, as well as an anomalous duct uniting the cyst to the right hepatic duct. As for the rest of the extrahepatic biliary canal, as well as the intrahepatic canal, nothing abnormal was noticed. The videolaparoscopic treatment consisted of a ligature with a clip of the cystic duct and the anomalous duct plus en bloc resection of the cyst and the gallbladder. Histopathologic study showed it to be a benign cyst and chronic calculous cholecystitis. It is important to establish the site of the cyst precisely before surgery, as the procedure should include its resection, since it could be the source of infection or development of lithiasis and even malignant degeneration. There are two hypotheses for the appearance of cysts in the biliary tract: congenital, due to a flaw in the multiplication of the cells that will form the biliary tract during the fetal life, and by aggression by pancreatic juice flowing back to the main biliary canal. The congenital origin seems to be the hypothesis that better explains the appearance of the cyst in the case described here, considering that the backflow of the pancreatic juice could hardly have occurred because of the anatomy as observed: the nonexistence of the common biliary-pancreatic canal and the valvular mechanism, present in the cystic canal, between the cyst itself and the confluence of the cystic canal into the main biliary canal, in addition to the anomalous biliary canal communicating the cyst to the right intrahepatie-canal.