In vivo biodistribution and PET imaging in A431- and NCI-N87-xenografted mice (high and low HER2 expression, respectively) demonstrated the preferred pharmacokinetic profile of [18F]SiF- and covalently-labeled affibodies, whereas [18F]AlF-NOTA(5)-ZHER2:2891 displayed minimal differentiation between the two tumor types, higher kidney retention and increased bone uptake in time. This evidence concerns the gene ERBB2 and neoplasm.