Objective: Bile duct tumor thrombosis in hepatocellular carcinoma (HCC) is a relatively rare event with a poor prognosis. Furthermore, bile duct tumor thrombus in HCC may be misdiagnosed when only imaging modalities are used. The efficiency of peroral cholangioscopy (POCS) in evaluating bile duct lesions has been reported.Patients: We present three cases of HCC with bile duct strictures in which POCS was performed as a preoperative evaluation.Results: In these three cases, diagnosing whether the lesion was a bile duct tumor thrombus on CT and endoscopic retrograde cholangiopancreatography was difficult. We performed POCS in three cases and were able to diagnose the presence of bile duct tumor thrombus of HCC, including differentiation from extrinsic compression of the bile duct.Conclusion: POCS for HCC with bile duct features is useful for the preoperative diagnosis of bile duct tumor thrombus, especially in cases where the surgical procedure depends on the presence of bile duct tumor thrombus.