Peliosis hepatis is a rare disease characterized by cystic hepatic sinusoidal dilatation and the presence of multiple blood-filled spaces in the hepatic parenchyma. In most cases, multiple lesions and individual cysts not exceeding 1cm in diameter occur. We report a case in which the condition occurred in a 33-year-old woman who presented with general weakness and in whom a 3.5 cm-sized single hepatic mass was discovered incidentally at ultrasonography. The radiologic features mimicked those of a signle hepatic mass.