Twenty patients with pathologically confirmed extraparenchymal intraabdominal lipomatous tumors, including two lipomas, two cases of diffuse infiltrating lipomatosis, and 16 liposarcomas, were examined by computed tomography (CT). The CT appearance of these tumors closely correlated with their gross and microscopic pathologic anatomy. Distinctive CT features differentiated simple lipomas from diffuse infiltrating lipomatosis and from liposarcomas. The densities of these tumors, including the variable densities of liposarcomas, were explained by their tissue composition. Lipomas, diffuse infiltrating lipomatosis, and lipogenic liposarcomas were predominantly of fat density, whereas myxoid liposarcomas were of a higher range of densities. Liposarcomas often contained more than one type of tumor tissue, resulting in masses of distinctly different densities coexisting within the same tumor. CT accurately depicted the presence, location, and size of the tumors and provided information about their relation to adjacent structures.