In this work, densities of the systems dimethyl sulfoxide (DMSO) + choline acetate and DMSO + 1-ethyl-3methylimidazolium acetate were measured with a Stabinger densimeter. The density was measured at temperatures T = [293.15, 373.15] K and for the full composition range when possible. Excess molar volumes and excess isobaric expansion coefficients were calculated for the latter system. The excess molar volume was correlated with the Redlich-Kister polynomial equation. Melting points of some mixtures of choline acetate + DMSO were also determined.