Results are presented from measuring the microwave dielectric properties of aqueous solutions of 1,3-dioxolane and 2,2-dimethyl-1,3-dioxolane-4-methanol at seven frequencies in the range of 5-25 GHz and temperatures of 288, 298, and 308 K. The static dielectric constants are considered, along with the times and parameters of activation of the dielectric relaxation process. Differences between hydration-induced changes in water and the effects of interaction between different groups of molecules are established for the solutions of the considered compounds. The dynamics of water molecules in solution is slowed, compared to that in pure water in both cases. It is established that this slowing is due to different molecular mechanisms of interaction between the dissolved species and the tetrahedral network of the H-bonds of the initial water.