Compared with the stomach and small intestine, the colon and rectum are uncommon sites of lymphomatous involvement. Primary colorectal lymphoma is diagnosed when the lesion is confined to the colorectal area and regional lymph nodes, without involvement of other organs including the upper gastrointestinal tract, bone marrow, and distant lymph nodes. The radiologic appearance of primary lymphoma of the stomach and small bowel is well known, but in cases involving the colorectal area, this is not so. In this article, we categorize and illustrate the radiologic manifestations of primary colorectal lymphoma according to the findings of double-contrast barium enema and CT images, and describe the pathologic findings.