New and improved compounds for use in diagnostic imaging or therapy having the formula M-N-O-P-G, wherein M is an optical label or a metal chelator (in the form complexed with a metal radionuclide or not), N-O-P is the linker, and G is the GRP receptor targeting peptide. Methods for imaging a patient and/or providing radiotherapy or phototherapy to a patient using the compounds of the invention are also provided. Methods and kits for preparing a diagnostic imaging agent from the compound is further provided. Methods and kits for preparing a radiotherapeutic agent are further provided.
