A prior study has shown for a vinyl ester resin that the adequate choice of the curing conditions becomes completely necessary to reach the maximum glass transition temperature. In the same study, the Variations produced in the dynamic mechanical properties because of exposure to different solvents were related to the chemical structure of both the resin and solvent. This investigation was undertaken in an attempt to analyze the effects of solvent exposure on the viscoelastic properties of resins currently used for applications in which the resin is kept in contact with the solvents. Several vinyl ester resins as well as various unsaturated polyester resins immersed in different liquids were investigated. The influence of exposure time to the solvent as well as that for the temperature were characterized using dynamic mechanical analysis. The chemical structure of the resin was found to be determinant in the changes produced after solvent exposure.