Abstract: Objective: To explore the imaging features of primary central nervous system lymphomas(PCNSL) by CT and MRI.Methods: The imaging data of CT and MRI of 19 patients with pathologically proved PCNSL were retrospectively analyzed.Results: Fourteen cases had single lesion and 5 had multiple lesions.A total of 31 lesions were detected.Twelve lesions were on the surface of the brain,13 were about the ependyma and 6 in the depth of the brain.Twenty-six lesions were detected by CT,with a detection rate of 83.9%.Thirty-one lesions were detected by MRI,with a detection rate of 100%.T₁WI and T₂WI showed that the intensity of the tumor was similar to the gray matter and 22 lesions were homogeneous and 9 were inhomogeneous.Enhancement showed that 80.6% lesions were remarkably matter-enhancing,16.1% lesions had enpendymal or meningeal enhancement.The perifocal white matter edema and the mass effect were mild to moderate in most cases.Conclusions: CT combined with MRI findings can help to make preoperative diagnosis in most cases;however diagnosis of rare atypical cases is difficult.