Lecture : Introduction: Among benign hepatic tumors, intraductal papillary neoplasm of the bile duct (IPNB) and mucinous cystic neoplasm of the liver (MCN) present cyst formation. Although both diseases are premalignant, they can develop into invasive carcinoma. Furthermore, simple cyst, which is most popular cystic lesions, are frequently treated by fenestration, and therefore, it is important to differentiate IPNB and MCN from simple cyst, not to perform fenestration for patients with the two cystic lesions. In this presentation, proper management of benign hepatic tumors with cyst formation is discussed. Patients: Thirty-three patients out of 2046 patients, who had undergone hepatic resection at my department between April 2000 and September 2019, underwent hepatic resections for cystic lesions of the liver. There were 14 males and 19 females with a mean age of 65 years. Results: IPNB was diagnosed preoperatively in 26 patients, simple cyst in 5 and MCN in 2. All patients underwent hepatic resections. Pathological diagnoses of the 26 patients with preoperative diagnoses of IPNB included IPNB in 16, simple cyst in 6, abscess in 2, MCN in 1 and embryonal sarcoma in 1. Protruding lesions were observed in 2 patients with IPNB and in one with MCN, and intrahepatic bile duct stones in 2. Six patients with simple cyst appeared to have septum formation, leading to preoperative diagnoses of IPNB. 9 patients were diagnoses as having high-grade IPNB and 2 were as having IPNB with associated invasive carcinoma. Five patients with simple cyst were pathologically confirmed to have simple cyst. Two patients with preoperative diagnoses of MCN were diagnosed as having MCN in 1 and simple cyst in 1, respectively. The sensitivity, specificity and accuracy for IPNB were 100%, 41% and 70%, respectively and those for MCN were 50%, 97% and 94%, respectively. Bile fistula was observed in 1 patient. Conclusion: In spite of advancement of diagnostic imaging modalities, it is still difficult to differentiate simple cyst with appearance of having septum formation from IPNB and MCN. Otherwise, diagnosis of IPNB and MCN can be made correctly, contributing to receiving adequate management by hepatic resection.