Abstract: Radiotherapy is a safe and effective management strategy for a variety of intracerebral tumors. ¹⁸F-FDG PET can provide information about the biologic characteristics of malignant cells and differentiate recurrent tumor from radiation necrosis, the sensitivity and specificity of FDG PET is 80% to 90% and 40% to 100%. ¹⁸F-FDG PET can predict the survival in high-grade recurrent gloima. The diagnostic and prognostic information can be provided by ¹⁸F-FDG PET. Co-registration of MRI or CT on a single computer may improve diagnostic accuracy of PET after radiotherapy for intracerebral tumors.