Primary lymphoma of the liver is a rare disease. In each of six cases, a large, often poorly defined mass of low attenuation was present within the liver. Four lesions originated in the right lobe and two originated in the left lobe. Satellite nodules were seen at presentation in one case and developed after presentation in two others. Other features, such as enhancement after contrast administration, necrosis, and calcification, were variable. Three of six lesions had areas of very low density, suggestive of necrosis. One mass had calcifications. After IV contrast administration, no enhancement occurred in three tumors, patchy enhancement occurred in two, and an enhancing ring was seen in the remaining tumor. The radiologic presentation of primary lymphoma of the liver differs from that of secondary involvement of the liver in systemic lymphoma. Whereas secondary lymphoma is often diffusely infiltrative and difficult to detect on CT, the lesions of primary lymphoma of the liver are easily identified on CT scans even before the administration of IV contrast material. Although rare, primary lymphoma of the liver should be included in the differential diagnosis of a large, hypodense liver mass on CT.