Abstract: Energy metabolism and amino acid transport and incorporation are important components of the pathophysiology of brain tumors. Combination of ¹⁸F-FDG and amino acid, especially ¹¹C-MET is more useful than single tracer in the field of brain tumor grading, differential diagnosis recurrent tumor from radiation necrosis and evaluation of prognosis. In addition, ¹¹C-MET is better than ¹⁸F-FDG in delineating tumor boundary, so it can provides more exact information in biopsy localization and planning of radiosurgery.