Castleman's disease is a rare disease characterized by lymph node hyperplasia. Although Castleman's disease can occur wherever lymphoid tissue is found, it rarely appears in the abdominal cavity, and is especially rare adjacent to the liver. Here, we report a rare case of Castleman's disease in the portal area that mimicked a hepatocellular carcinoma (HCC) in a chronic hepatitis B patient. A 40 year-old woman with chronic hepatitis B presented with right upper quadrant discomfort. Computed tomography and magnetic resonance imaging results showed a 2.2 cm-sized, exophytic hypervascular mass in the portal area. HCC was suspected. However, histologic examination revealed Castleman's disease. We suggest that Castleman's disease should be included as a rare differential diagnosis of a hypervascular mass in the portal area, even in patients with chronic hepatitis B.