Vibrational resonance is a dynamical counterpart of stochastic resonance whereby one replaces the external noise by a high frequency field. An optimal strength of this field may lead to enhancement of the response of the nonlinear system to a weak external field. We analyze the problem classically and then extend to quantum domain to calculate the linear and nonlinear response of a two-level system to a weak external periodic field to realize the significant enhancement of the second harmonic of the weak field as well the Raman lines.