Abstract: As the application of metabolic imaging are expanding, radio labeled amino acids may gain increased clinical interest.The fact that amino acid imaging is less influenced by inflammation may be advantageous in comparison with ¹⁸F-FDG PET imaging.In brain tumor, the diagnostic value of amino acid imaging is adequate.In most of other tumors, the data do not yet permit definitive conclusions, but the general feasibility of amino acid imaging has sufficiently been shown.More research is required in larger patient series and in well-defined clinical setting.This review mainly describes the basic aspects and clinical applications of ¹¹C-methionine, ¹¹C-tyrosine, and ¹²³I-iodomethytyrosine.