Objective To investigate diagnostic value of CT and MRI in abdominal and plevic demoid fibromatosis(DF). Methods To analyze the CT and MRI images of 13 patients with DF confirmed by operations and pathology retrospectively. Four patients underwent CT scan, 6 patients underwent MR scan,3 patients underwent both CT scan and MR scan. Results Seven cases of DF were located in the abdominal wall, 2 cases in the abdominal cavity, 4 cases in spatium intermuscula of pelvic crossed foramen ischiadicum majus or obturator spreading to the pelvic cavity. CT examination revealed: 7 cases with plain CT scan showed soft tissue density similar to muscle without calcification and necrosis, 3 cases with linear or reticular slightly high density, all tumors were homogeneous or heterogeneous enhancement. MRI examination revealed: compared with muscle, 7 cases showed inhomogeneous low signal and 2 cases homogeneous iso-signal on T1WI; all cases showed inhomogeneous high or slightly high signal and 7 cases with linear or reticular low signal area on T2WI. Eight cases showed moderately or obviously inhomogeneous enhancement, 1 case showed mild enhancement, and no enhancement in long T1 and short T2 signal area after contrast administration. Histopathologically, the arrangment of tumor tissue was composed of fiber cells and fibroblast arranged in cords and weaves, intercellular collagen tissue wrapping, and occasionally nuclear fission. Conclusion Demoid fibromatosis of the abdomen and pelvic have certain CT and MRI characteristics, which have important value for the preoperative diagnosis, but MRI is superior to CT, which could better show the internal structure of tumor and the relationship of peripheral nerve, blood vessel, deep organs around the tumor.