Geometries and energy separations of 27-low-lying electronic states of Rh3CO with different structures have been investigated. Atop, bridged, and threefold CO orientations with Rh-3 were considered. Complete active space multiconfiguration self-consistent field method (CASMCSCF) followed by large scale multireference singles and doubles configuration interaction (MRSDCI) computations that included up to 2.1 million configurations were used. Three nearly degenerate electronic states were found for the threefold structure around the minimum energy region. At the highest level of theory, the (2)A(2) state prevailed to be the ground state. The assignment of minimum energy states for the atop and bridged structures are unambiguous. The B-4(2) and B-4(1) electronic states were found to be the most stable states for these two respective geometries. The nature of the metal-CO bond formation in different states is discussed, and the difference density maps of Rh3CO with respect to Rh-3 and COs are presented. The dissociation energies and CO vibrational frequencies have been computed and the results are compared with the available experimental data.