Objective: To investigate value of diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC), fractional anisotropy (FA) in the prediction of radiotherapy (RT) responses for glioblastomas after surgical operations. Methods: Nineteen glioblastoma after surgery were examined by DWI before RT and at 30 Gy middle RT. ADC and FA values on DWIs both in the residual tumoral tissue and peritumoral tissue were measured before RT and at 30 Gy middle RT, and RT responses were classified as group of CR, PR, SD and PD by comparison, of pretreatment and postchemoradiotherapy scans. The correlation between the ADC and FA and treatment response of 4 weeks after the complement of RT was evaluated as well. Results: The ADC of the residual tumors was greater at 30 Gy middle RT than that before RT in CR group, and no obviously change at 30 Gy middle RT than before RT in PD group. The ADC of peritumoral tissue revealed dramatic increased at 30 Gy middle RT, and the FA of peritumoral tissue showed significant decreased at 30 Gy middle RT after RT in PD. Conclusion: Changes in ADC and FA of tumoral and peritumoral tissue may be helpful to predict the response of glioblastomas after surgery to RT.