The electronic and vibrational properties of CN- adsorbed on Ag electrodes have been studied through ab initio multiconfigurational self-consistent field (MCSCF) calculations of the molecular ions AgCN- and AgNC- and compared with PtCN- and PtNC-. Results of calculations are consistent with the experimental data obtained by in situ visible infrared sum frequency generation (SFG) spectroscopy of CN- adsorbed on polycrystalline Ag and Pt electrodes.