OBJECTIVE This pilot study made a preliminary attempt to distinguish different metabolic phenotypes of primary human brain tumors with dual tracer 13N-ammonia and 18F-FDG. METHODS 74 patients were included in this study including 12 benign meningiomas (B-MEN), 4 malignant meningiomas (M-MEN), 15 low-grade gliomas (LGG), 32 high-grade gliomas (HGG) and 11 primary central nervous system lymphomas (PCNSL). All patients underwent 13N-ammonia and 18F-FDG PET imaging. Semi-quantification analysis by tumor-to-gray matter (T/G) ratios was used for the evaluation of tracer uptakes. After the calculation of canonical discriminant functions, cross validation was done for all cases to evaluate the differential efficacy of dual tracers. RESULTS According to the visual analysis, B-MEN were characterized by lower uptake of 18F-FDG and higher uptake of 13N-ammonia, while PCNSLs displayed contrary results. Both M-MEN and HGG had higher uptake of 18F-FDG and 13N-ammonia, while LGG displayed negative results for both tracers. According to the T/G ratios analysis, the accuracy of predicted tumor classification by means of canonical discriminant analysis for B-MEN, LGG, HGG and PCNSL was 91.7 %, 100 %, 84.4 % and 93.3 % respectively; the overall accuracy was 90.5 %. CONCLUSIONS The combination of dual tracer 13N-ammonia and 18F-FDG has a certain potential in distinguishing different types of brain tumors (meningiomas, gliomas and PCNSL). However, an advantage of the additional use of 13N-ammonia PET compared to a combined diagnosis with MRI and 18F-FDG PET could not be demonstrated and requires further studies.