Peritoneal lymphomatosis is a rare manifestation of high grade lymphomas. Although it is difficult to differentiate peritoneal lymphomatosis from other peritoneal diseases such as peritoneal carcinomatosis and leiomyomatosis clinically and radiologically, it should be included in differential diagnosis because the disease is curable with chemotherapy. Consequently, radiologic diagnosis plays a very important role in the detection of this disease. We experienced two cases of peritoneal lymphomatosis with primary gastrointestinal lymphomas in the distal ileum. The two patients were 25 and 50-year-old males. Abdominal CT, ultrasound and barium study were performed on both patients. Both patients had non-Hodgkin's lymphoma confirmed with open or sonographically guided biopsies. Although radiologic appearances overlapped, characteristic findings of long-segmental circumscribed annular mass, aneurysmal luminal dilatation, small to moderate amount of ascites without septation or loculation, diffuse involvement of mesentery, omentum and peritoneum, and enlarged lymph nodes were helpful in narrowing the range of possible diagnoses.