The results of studying the influence of the content of Ca2+, Mg2+, Na+, and K+ cations in water on the level of lipid peroxidation products and antioxidants in the tissues of bivalve mollusks, D. bugensis and D. polymorpha, are presented. Mollusks were caught in four water areas of the Gorky Reservoir, which differ in the concentrations of Ca2+, Mg2+, Na+, and K+ cations. A correlation relationship has been established between the quantitative parameters of cations in water and the intensity of peroxide processes, on the one hand, and the level of general antioxidant activity in mollusk tissues, on the other. Statistically significant interspecific differences in the studied parameters have been recorded in mollusks from areas with an increased concentration of cations.