The densities of solutions of bicaret (2,4,6,8-tetraethyl-2,4,6,8-tatraazabicydo[3.3.0]octane-3,7-dione or tetra-N-ethylglycoluril) in ordinary (H2O) and heavy (D2O) water were measured using the Anton Paar DMA 5000 M high-precision vibrating tube densimeter. All experiments were carried out between 278.15 K and 318.15 K at pressure to be ca. 0.1 MPa. The solution molality ranged from approximately (0.01 to 0.2) mol.(kg of solvent)(-1) for each of H/D isotopically distinguishable systems compared. The temperature-dependent apparent molar volumes as well as expansibilities (down to infinite dilution) of the solute were derived from density data. The behavior of D2O H2O solvent isotope effects on the considered quantities was described taking into account the structural features of H2O and D2O media. The obvious relationship between D2O-H2O solvent isotope effects on the standard molar volume of bicaret and standard molar enthalpy of its dissolution in water was discovered. One of the points of this work is a comparison of the obtained volumetric characteristics with those for tetra-N-methylglycoluril (mebicar), using the previous data.