Hepatobiliary cystadenomas are rare tumors that are difficult to diagnose preoperatively. They can reach large sizes that make them real intraoperative “surprises”. A 63-year-old woman, presented with a symptomatic huge abdominal cystic mass, underwent complete resection of the mass with safety margins. Histopathological report revealed mucinous hepatic cystadenoma with “ovarianlike” stroma and areas of sclerohyalinization. The differential diagnosis of the large cystic tumors which occupy the right hemiabdomen must include the biliary cystadenoma; the complete resection of the tumor with safety margins avoids local recurrence, and therefore represents the optimal therapy because of the malignant potential of the disease. The postoperative follow-up includes abdominal ultrasound or CT scan and CA 19-9 measurement. Hepatobiliary cystadenomas are rare tumors that are difficult to diagnose preoperatively. They can reach large sizes that make them real intraoperative “surprises”. A 63-year-old woman, presented with a symptomatic huge massive cystic mass, underwent complete resection of the Mass with safety margins. Histopathological report revealed mucinous hepatic cystadenoma with “ovarianlike” stroma and areas of sclerohyalinization. The differential diagnosis of the large cystic tumors which occupy the right hemiabdomen must include the biliary cystadenoma; the complete resection of the tumor with safety Margins avoids local recurrence, and therefore represents the optimal therapy because of the malignant potential of the disease. The postoperative follow-up includes abdominal ultrasound or CT scan and CA 19-9 measurement.