The mechanism of the title reaction has been investigated using density functional and coupled cluster calculations. The results indicate that the lowest energy path corresponds to the eta(2)co coordination of CO2 followed by the insertion of Sc into a C-O bond. We show that two doublet state ((2)A' and (2)A") potential energy surfaces have to be considered to describe the reaction mechanism. On the 2A' surface, the reaction gives a weakly bound OScCO species that can easily dissociate into ground state ScO((2)Sigma(+)) + CO products, whereas the 2A" state insertion complex is thermodynamically stable because it correlates to an excited state of ScO. The applicability of the B3LYP and CCSD(T) methods for the relative stability of intermediates is examined, and our results are related to available experimental findings.