Peritoneal lymphomatosis, a rare presentation of lymphoma, can mimic peritoneal carcinomatosis. Computed tomography findings in both conditions include omental caking, as well as peritoneal enhancement, thickening and nodularity. We report three cases of peritoneal lymphomatosis and give an analysis of the salient imaging features that aided in the accurate diagnosis of the condition in each case. Two of the three cases demonstrated elevated serum cancer antigen 125 levels, a marker commonly associated with ovarian carcinoma. It is thus critical to distinguish peritoneal lymphomatosis from carcinomatosis, as the prognosis and management are dramatically different.