Specific interactions in blends of salts of sulfonated polystyrene and poly(ethylene-co-vinyl acetate) (EVA) were studied as a function of the blend composition, metal cation (H+, Na+, Zn2+) and sulfonate content. Intermolecular association between zinc sulfonate polystyrene (ZnSPS) and EVA in solution was evidenced by increase in the reduced viscosity of the blend relative to that of the pure EVA. Interactions in the solid state were observed in terms of a shift to lower frequencies in the in-plane stretching vibration of benzenesulfonate. Analysis by infrared spectroscopy indicated that the EVA solvated the Zn2+ decreasing the ionic associations in the blends. This effect increases when the ion content of ZnSPS increases and led to improvement in the dispersion of the polymeric phases as compared with that in the sodium sulfonate-PS/EVA sulfonic acid-PS/EVA and PS/EVA blends.