Abstract: As the applications of metabolic imaging are expanding, radiolabeled amino acids has gained increased clinical interest. It is necessary to understand the basic aspects of amino acid metabolism and radiolabeled|and finally describe in the tumors. Have been most used clinically, such as, ¹¹C-methionine, ¹¹C-tyrosine and ¹²³I-iodomethyltyrosine. And the theoretic and clinical back-ground of amino acid imaging is clear and is fit for clinical applications. Contrasting with the ¹⁸F-FDG PET suggested that is less troubled by interfering uptake in inflammatory tissues. There is a more accuracy in the brain tumors specially. In the other tumor types has been shown sufficiently.