Abstract: Objective : To explore the potential value of diffusion-weighted magnetic resonance imaging (MRI) incharacterizing soft-tissue tumors. Methods : Diffusion-weighted MRI was performed in 43 histologically provensoft-tissue tumor cases using diffusion-weighted spin-echo sequences. Of the 43 soft-tissue tumor cases,there were 25 cases of sarcoma and 18 cases of benign tumor. The b values of diffusion were 0 and 500 s/mm². The apparent diffusion coefficient (ADC) values of a large region with no necrosis, scar tissue, hemor-rhage or calcification representing the lesion were measured. ADC values of benign tumors, malignant tumorsand normal muscles were compared. ADC values of different histological malignancy (grade Ⅱ, Ⅲand Ⅳ)were compared. Three patients with malignant tumors (2 cases of primitive neuroectodermal tumor and 1case of rhabdomyosarcoma) underwent diffusion weighted MRI before and after chemotherapy. We evaluatedthe changes in ADC values. Results : The ADC values of the malignant tumors (mean±SD, 0.96±0.31×10^-3mm²/s) were significantly lower than those of benign lesions (1.92±0.63×10^-3mm²/s) and muscles (1.69±0.47×10^-3mm²/s). There was no significant difference in ADC values between benign lesions and muscles. High sensitiv-ity (92%) and specificity (83%) were obtained when the ADC value was 1.38×10^-3mm²/s in the differentiationof benign and malignant tumors. No significant difference was found in ADC values among groups of differenthistological grades of malignancy. In the 3 patients with malignant tumors who underwent diffusion-weightedMRI before and after chemotherapy, ADC values after treatment of 2 cases were increased due to mi-cro-necrosis but there were no obvious changes in the other case. Conclusion : Diffusion-weighted MRI has po-tential value in differentiating benign soft-tissue tumors from malignant ones. The increase of ADC values ofsoft-tissue sarcoma after chemotherapy warrants further studies of diffusion weighted imaging and histologi-cal assessment for evaluating therapeutic reaction.