Castleman's disease is an uncommon lymphoproliferative disorder, which occurs most commonly in the mediastinum. Sporadic reports of its occurrence in the hepatoduodenal ligament, and other extrathoracic locations have also been documented. Ultimately, Castleman's disease can develop anywhere lymphoid tissue is found, and the preoperative diagnosis is often difficult. We report a case of hyaline vascular-type Castleman's disease in the hepatoduodenal ligament. An asymptomatic 26-year-old woman was admitted to our hospital for further examination of a mass found on ultrasonography. A contrast-enhanced computed tomography (CT) scan confirmed a hypervascular mass in the hepatoduodenal ligament, and angiography showed that the mass was receiving its blood supply from various arteries. These findings suggested a diagnosis of Castleman's disease and we removed the tumor without resecting any other organs. CT and angiography were helpful in establishing a correct preoperative diagnosis, which minimized the magnitude of surgery.