Densities of aqueous solutions of achiral 1,3-dimethylglycoluril (1,3-DMGU) and 1,3-diethylglycoluril (1,3-DEGU) were measured using a hermetically sealed vibrating-tube densimeter, with an uncertainty of 1 . 10(-5) g . cm(-3), at T = (278.15, 288.15, 298.15, 308.15, and 318.15) K and p = (99.6 +/- 0.8) kPa. The solute molality was ranged from (0.06 to 0.39) and from (0.01 to 0.07) mol . kg(-1) for the aqueous 1,3-DMGU and 1,3-DEGU, respectively. The standard (at infinite dilution) molar volumes and isobaric expansibilities for the 1,3-dialkyl-N-substituted glycolurils compared in water were calculated and discussed in comparison with the previously derived molar enthalpies and heat capacities of their dissolution (hydration). The temperature-dependent behavior of packing-related hydration effects was described taking into account the structural features of a solute molecule. (C) 2015 Elsevier Ltd. All rights reserved.