Hepatobiliary fibropolycystic diseases are a unique group of entities involving the liver and biliary tract, which are caused by abnormal embryologic development of the ductal plates at various stages. We experienced strange hepatobiliary fibropolycystic diseases with a complex mass composed of malformed ducts and biliary cysts, which did not belong to, and were different from, previously known malformations. They were unique in imaging and histologic features. We herein report three cases of monosegmental hepatobiliary fibropolycystic disease mimicking a mass.