Agenesis of the gallbladder and the cystic duct is one of the rarest congenital abnormalities of the biliary system. Almost half of the patients develop common duct stones and 23% of them manifest signs and symptoms that mimic biliary colic. We present two cases of gallbladder agenesis. The first case is of a woman presenting symptoms of biliary colic. Laparoscopy failed to reveal either gallbladder or cystic duct. The procedure was continued to further search for ectopic sites of gallbladder. A gallbladder agenesis was suspected and then confirmed via post-operative magnetic resonance cholangio-pancreatography, who also objectified a cystic dilatation and septum of the main bile duct. The second case is of a woman with symptoms of biliary colic. A first abdominal ultrasonography objectified a "scleroatrophic" gallbladder; on the second ultrasonography a gallbladder agenesis was suspected and later confirmed via magnetic resonance cholangio-pancreatography. We report through these cases our experience with regard to the challenges associated with the diagnosis and management, and a brief review of the literature of this rare pathology.