Abstract: Radiopharmaceuticals comprising molecules that target to N-formyl-methionyl-leucyl-phenylalanine (fMLF) receptor on leukocytes in order to target sites of inflammation for diagnostic imaging are described. The targeting molecules are attached to capping groups that make the entire molecule either antagonists or weak agonists of fMLF receptor and therefore do not elicit a chemotactic response resulting in neutropenia. The preferred targeting molecule is ReO-Gly-lys(Dimethylgly-t-Butylgly-cys-gly)-glu-trp-phe-leu-nle-NHCOcyclopropyl. The invention also relates to the use of combinatorial chemistry to obtain preferred molecules that target sites of inflammation for diagnostic imaging.