In this work, the miscibility of poly(2-chlorostyrene) (P2CS) and poly(vinyl methyl ether) (PVME) mixtures was characterized and compared to polystyrene (PS)/PVME blends. It was found, by light scattering, that P2CS/PVME blends exhibit a lower critical solution temperature. Fourier transform infra-red spectra of these two blends indicate that the presence of the chlorine atom strengthens the attraction between the phenyl rings of P2CS and the electron lone pairs of the oxygen atoms on the PVME chains. This specific interaction is the main reason for the improvement of the miscibility of this particular blend in comparison to PS/PVME. These experimental results are in accord with the magnitudes of the binary interaction parameters, chi, of P2CS/PVME and PS/PVME blends estimated from the cloud point data based on the mean-field theory. The experimental results obtained in this work provide a molecular basis for the interpretation of polymer-polymer miscibility.