Objective: To investigate the clinical, imaging and pathological findings of the primary (CNS) lymphoma in patients without AIDS. Methods: The clinical, laboratory, neuroradiological and pathological data of such 15 cases were analysed. Results: The clinical features of the primary malignant lymphoma of CNS are variable, however, more than half of patients were presented with an increased intracranial pressure and a neurologic dysfunction, such as weakness of limbs, speech changes and seizures. These symptoms were always misdiagnosed as some other tumors. Examination of CSF revealed a mild or intermediate increase of protein in all patients by way of lumbar punctures. Imaging examinations by CT and MRI both showed solitary or multiple masses of tumor located more likely in the frontal and temporal lobes. Only 20% patients mimicked the demyelinating disease and were misdiagnosed as multiply sclerosis. Conclusion: Patients with such CNS lymphoma usually do not present the characteristically clinical manifestations or findings in the imaging scanning. Brain biopsy may be a method more reliable to confirm this disease and be important for improving the prognosis of patients.