This study investigates the influence of carboxylic monomers, such as itaconic acid (IA), on the colloidal properties of the latexes made by semicontinuous emulsion copolymerization of styrene (STy) with n-butyl acrylate (BA). A number of copolymerization runs were carried out with different IA concentrations. The effect of functional monomer on the overall conversion, the colloidal properties of the latexes, and the distribution of the carboxylic groups (buried, particle surface and aqueous phase) were examined. The carboxylic groups present in the latexes were analyzed using conductimetric and potentiometric titrations. The behavior of the IA on the wet scrub resistance of highly pigmented paints for architectural coatings was examined and correlated with the distribution of the carboxylic groups. The results obtained showed that the properties of highly pigmented paints are greatly dependent on the amount and distribution of the carboxylic groups. The carboxylic acid distributed in the aqueous phase has a strong influence on the wet scrub resistance and on the characteristics of the final products.