PURPOSE: To assess the usefulness of diffusion-weighted MR imaging in patients with intracranial tumors. MATERIALS AND METHODS: Using the single-shot spin echo EPI technique on a 1.5T unit and two gradient steps(b values of 0, 900 s/mm2), diffusion-weighted MR images (DW-MRI) of 76 patients with various intracranial tumors including high-grade glioma (n=20), meningioma (n=15), metastasis(n=14), lymphoma (n=6), low-grade glioma (n=5), schwannoma (n=4), cerebellar hemangioblastoma (n=3), - and others- were obtained. The signal intensity of each tumor was visually assessed as one of four grades, and this and apparent diffusion coefficient(ADC) were analyzed in the solid and cystic portions of tumors, normal gray matter, white matter and CSF. RESULTS: Lymphomas, metastases, meningiomas, and high- and low-grade gliomas showed low ADC values in increasing order. Tumors showing high signal intensity on DW-MRI had low ADC values. Visual assessment whowed that solid portions of high-grade gliomas were significantly more hyperintense than those of low-grade gliomas. There was, however, no significant difference in ADCs between high- and low-grade gliomas. Lymphoma a and metastases showed significantly higher signal intensities on DW-MRI and lower ADCs than did high-grade gliomas. There were significant differences in signal intensities, as seen on DW-MRI, and in ADCs, between metastatic adenocarcinomas and non-adenocarcinomas. Schwannomas and cerebellar heman-gioblastomas showed low signal intensities and high ADC values. CONCLUSION: DW-MRI appears to provide an additional means of examining intracranial tumors, not available with conventional MRI, and may thus be helpful in the grading of gliomas and the differential diagnosis of some intracranial tumors.