This research aimed to develop new tumor targeted theranostic agents taking advantage of the similarities in coordination chemistry between technetium and rhenium. A gamma-emitting radioactive isotope of technetium is commonly used in diagnostic imaging, and there ate two beta(-) emitting radioactive isotopes of rhenium that have the potential to be of use in, tacliothetapy. Variants of the 6-hydrazinonicotinamide (HYNIC) bifunctional ligands have been prepared by appending thioainide functional groups to 6-hydrazinonicotinamide to form pyridylth-, iosernicarbazide ligands: (SHYNIC). The new bidentate ligands were conjugated to the tumor targeting peptides Tyr(3)-octreotate and cyclic-RGD. The new ligands and conjugates were used to prepare well-defined {M=O}(3+) complexes (where M = Tc-99m Or Re-nat or Re-188) that feature two targeting peptides-attached to the single metal ion. These new SHYNIC ligands are capable of: forming well-defined rhenium and technetium complexes and offer the possibility of using the Tc-99m imaging and Re-188/186 therapeutic matched pairs.