Cystadenomas of the pancreas are relatively rare compared to pseudocysts. There are two types of cystadenoma of the pancreas; mucinous and serous. Serous cystadenomas of the pancreas are very rare. We experienced a serous cystadenoma located in pancreatic tail. The patient was male, forty-one years old, and was free from any subjective symptom. The pancreatic cyst was found by abdominal ultrasonography and was difficult to differentiate serous or mucinous by computed tomography or celiac angiography preoperatively. We performed distal pancreatectomy and the cyst was revealed to be serous cystadenoma pathologically.