Small peptide-based compounds have attracted an enormous interest as carrier molecules to selectively deliver radionuclides to target tissues, sparing critical normal organs. When looking for "matched pairs" of radionuclides,suitable for radiolabeling of peptides for diagnosis and therapy, technetium and rhenium represent an almost ideal constellation. The important role of technetium-99m and Re-186/188 is based on the decay characteristics, suitable for tumor diagnosis and therapy. Tc-99m and Re-188 are readily available by either a 99Mo/99mTc or the 188W/188Re radionuclide generator system. Furthermore, technetium and rhenium are chemically related and share structural as well as reactive similarities, which prompt an attractive "matched-pair" situation. This article shows an overview of 99mTc-and 186/188Re-radiolabeled peptides that have been tested for their potential use as imaging and therapeutic agents in oncological diseases.