The lifetime for the CN- stretching mode has been measured at a polycrystalline Cu and Cu(111) electrochemical interface with difference frequency generation. The lifetimes on both surfaces are similar to17 ps, show no definitive trend with electrochemical potential, and are similar to those reported for the CN-/Au system. When all experimental lifetimes for CN-on metals are considered, a trend is noted between vibrational lifetime and the onset of metal interband transitions.