Objective To explore the impact and value of 11C-MET PET/CT for high-grade glioma in making conformal radiotherapeutic planning compared with MRI.Methods From October 2011 to September 2013,11C-MET PET/CT and MRI were performed in 25 initial glioma cases and 9 recurrent cases.All 34 cases (19 males,15 females) were classified into initial group (n=17),initial surgery group (n=8) and recurrent group (n=9).GTV was outlined using PET/CT images combined with T1 weighted MRI images.Results 11 C-MET PET/CT optimized radiotherapy targets in 22 cases,including 7 initial cases,8 initial surgery cases and 7 recurrent cases.GTV was consistent with the volume of abnormally enhanced region on T1 weighted MRI (VMRI) in 10 initial cases,GTV＞VMRI in 5 cases,and GTV＜VMRI in 2 cases.GTV＜VMR1 in the initial surgery group.GTV was consistent with VMRI in 2 recurrent cases,GTV＞VMRI in 2 cases and GTV＜VMRI in 4 cases; 1 recurrent case's GTV located largely outside the VMRI.Conclusions There are some differences on locating the lesions of high-grade gliomas between 11C-MET PET/CT and MRI.Using 11CMET PET/CT in sketching radiotherapy target could significantly optimize the high grade glioma's radiotherapeutic planning,which may be more valuable in recurrent or operative cases.