A radiopharmaceutical for diagnostic imaging containing as an active ingredient a technetium-99m nitride heterocomplex comprising technetium-99m nitride and two different ligands coordinated therewith, i.e., a bisphosphinoamine compound as a .pi. electron acceptor and a bidentate ligand as a .pi. electron donor and represented by the following formula (I): [.sup.99mTc(N)(PNP)(XY)].sup.+ (I)wherein .sup.99mTc(N) is technetium-99m nitride, PNP is a bisphosphinoamine compound and XY is a bidentate ligand, is markedly accumulated in heart and adrenal glands and hence is useful for radiodiagnostic imaging of heart and adrenal glands.
