The aim of this study was to determine the uptake of L-[methyl-11 C]-methionine ( 11 C-MET) in the normal brain of patients younger than 20 y, to facilitate more accurate diagnoses in young patients. Methods: Eighty-two patients were categorized into 4 groups according to their age. They underwent 11 C-MET PET, and a standardized uptake value (SUV) was determined for different brain regions including the frontal lobe, parietal lobe, cerebellum, and brain stem. Results: Compared with all other parts of the brain, the cerebellum had the highest SUV. A tendency for a positive relationship between SUV and age was found in all regions, and a significant relationship with SUV was found in the frontal lobe and cerebellum. Conclusion: The character of SUV in the normal brains of children is different from that of adults, and these normal SUV data will play an important role as a critical reference value.