We report the difficult diagnosis of a rare case of bile duct cystoadenocarcinoma of the liver. A 61-year-old man was referred to our hospital because of an intra-abdominal tumor . An abdominal ultrasonography examination demonstrated a tumor (13x10cm) with mixed hyperechoic and hypoechoic areas that was located adjacent to the left lobe of the liver. Color Dopplar sonography showed a weak signal in the tumor. A gastroscopy revealed a tumor extendeding throughout the gastric antrum of the stomach. An abdominal computed tomography examination revealed a left hepatic tumor(13.3x11.4cm) with low-density heterogeneity. We performed an open extirpation of the tumor using a left lateral segmentectomy in June 2008. The resected specimen measured 18x15x12cm and weighed 1500g (including the liver tissue that was resected with the tumor). A histopathological study revealed mucin, calcification and tubular patterns characteristic of the growth of adenocalcinoma cells. The pathological diagnosis was a bile duct cystadenocarcinoma in the left liver. We report this case and review the relevant medical literature.