The procedure of analysis of harmonic waves propagate in elasticwave guides is applied to harmonic waves in linear viscoelastic wave guides. The formal solutions which satisfy the frequency equations of guides wave motions in a linear viscoelastic plate are thus obtained. The frequency spectra of guided waves in a viscoelastic plate are compared with those of elastic waves, and their differences are discussed. The displacement and the phase lag profiles in L and SV modes are obtained at specific frequencies, and it is shown that the viscoelastic waves of these modes are not plane waves.