The vibrational level mixing at the second CH stretch overtone state CH(v = 3) in benzene has been studied quantum mechanically using a completely symmetrized vibrational basis set in terms of a combined local mode/normal mode description. The employed symmetrized approach has helped to reduce the dimensionality of coupling Hamiltonian matrices and thus allowed for the inclusion of all 30 vibrational modes in the calculations. The absorption spectrum and dynamical intramolecular vibrational redistribution characteristics for initial excitation of a symmetrized local mode ''bright'' state in the CH(v = 3) overtone manifold have been calculated and analyzed in connection with the degree of localization of the CH stretch overtone vibrational system in benzene.