Tie-line data for two quaternary systems of (water + 1-butanol + diethyl carbonate (DEC) + dimethyl carbonate (DMC)) and (water + 1-butanol + hexane + DMC) and two relevant ternary systems of (water + 1-butanol + DEC) and (water + 1-butanol DMC) at T = 298.15 K and atmospheric pressure were determined. The experimental ternary and quaternary (liquid + liquid) equilibrium results were correlated by using the modified universal quasichemical activity coefficient (UNIQUAC) model, and the interaction parameters were obtained. The root-mean-square deviations of the two quaternary systems correlations were 0.56 % and 0.75 %, respectively. Distribution coefficients were calculated to evaluate the solubility of DMC in two phases.