Sigma-2 (σ 2) receptors have been proposed to be the progesterone receptor membrane component 1. Progress in cancer biology has revealed that (σ 2) receptors are over-expressed in many types of cancer. The expression of (σ 2) receptors is assumed to be a suitable biomarker of cellular proliferation in solid tumors . In our previous work, we used PB28 as lead compound to design novel 99m Tc cyclopentadienyl tricarbonyl complex as putative agent for (σ 2) receptor tumor imaging . In this abstract, RHM-1, another (σ 2) receptor selective ligand, was used as lead compound to design novel [(Cp-R) M (CO) 3](M= Re, 99m Tc) complexes as potent (σ 2) receptor ligands. Synthesis and preliminary evaluation of these complexes are reported.