Results of thermodynamic calculations of the interactions of radon waters from the Zaeltsovsky field with the minerals of host rocks are presented for the first time. It was established that waters under study are supersaturated with respect to calcite and siderite, and to a smaller extent with respect to magnesite and dolomite. No saturation of radon waters with respect to primary aluminosilicate minerals (albite, anortite, microcline, ferrosilite) is observed. The points are located in the fields of stability of clayey minerals (kaolinite, Ca- and Mg-montmorillonite, Fe-sepiolite), gibbsite and leptochlorite. In the evolution of the water-rock system, they correspond to the siallite type of interaction with rocks.