Two patients presented with provisional diagnoses of glioma. Computed tomography (CT) and magnetic resonance imaging failed to show the boundaries of the tumor clearly. Positron emission tomography (PET)/CT with [(18)F]fluorodeoxyglucose and (11)C-methionine clearly showed the location, extent, and heterogeneity of the tumors. The tumors were resected under PET/CT neuronavigation guidance. Histological examination of the specimens showed that PET/CT neuronavigation provided reliable distinction between normal brain and glioma, and that the uptake of PET tracers can indicate the degree of proliferation.