Densities of dilute solutions of 1,3-dimethyl-2-imiazolidinone in H2O and D2O, with the solute mole-fractions ranging up to 0.01, have been measured with an error of 1.5 . 10(-5) g . cm(-3) at (278.15, 288.15, 298.15, 308.15, 313.15, and 318.15) K and atmospheric pressure using a vibrating-tube densimeter. The partial molar volumes of the dissolved DMI (down to the infinite dilution) and solvent (H2O or D2O) as well as the excess molar volumes of the isotopically distinguishable solutions have been calculated. The effects of the solvent isotope substitution, solute concentration and temperature on the volume changes caused by DMI hydration have been considered. The obvious relationship between the D2O-H2O solvent isotope effects on the partial molar volume and enthalpy of solution of DMI has been discovered. (C) 2009 Elsevier Ltd. All rights reserved.