Abstract： Objective To evaluate the role of 11C-methionine positron emission tomographv(MET PET-CT)in differentiating tumor recurrence from radiation necrosis in brain slioma patients.Methods From June 2008 to September 2009,30 brain glioma patients with suspected tumor recurvence or radiation necrosis after radiotherapy were evaluated by MET PET-CT.The median time between initial radiotherapy and PET examination was 13.5 months.Tumor recurrence were confirmed by histological analysis while necrosis was based on histological analysis or the subsequent clinical follow-up.Results Eighteen out of 19 patients were histologically confirmed tumor recurrence among those tumor recurrence shown by MET PET-CT after surgery or stereotactic biopsy.11 patients were considered to have radiation necrosis because of stable neurological sympotoms and without massive enlargement of the lesion during the after follow-up.The sensitivity,specificity and accuracy of MET PET-CT for detecting tumor recurrence were 100%,91.7%and 96.7%respectively.Conclusion MET PET-CT is a powerful tool in differentiating brain tumor recurrence from radiation necrosis after radiotherapy.