Zero-point energy excitation has a profound effect on the relaxation of benzene CH and CD overtone states. Only adding a fraction of the zero-point energy for each normal mode in the initial conditions results in smaller overtone relaxation rates. If no zero-point energy is added to C 6H6, the n = 3 and 5 CH overtones do not relax within 1 ps. Adding zero-point energy to different types of normal modes has nonequivalent effects on overtone relaxation. Zero-point excitation of modes with HCC bend character is particularly effective in enhancing relaxation of the overtones.