In the present work we have studied the changes in the FWM signal response considering the modification in the longitudinal and transversal relaxation times T1 and T2, respectively. These changes are obtained considering three cases of rate between longitudinal and transversal relaxation times T1/T2, with three orders of magnitude between them: a) 0.1, b) 1 and c) 10. These modifications are applied to push-pull molecules, taking into account the valence-bond charge-transfer model. Moreover, we have taken into account the symmetric values of Vo = ± 1 (corresponding to the electronic energy gap between the states involved in the model). Notable changes in maximal intensity of the peaks belong to the FWM spectrum are observed with the variation in the ratio between the relaxation times.