Adsorption of Ca(II) and Fe(III) ions at the SnO₂/NaCl solution interface as well as the effect of adsorption on the structure of electrical double layer were presented in this paper. The influence of ionic strength, pH and presence of ions on adsorption of Ca(II) and Fe(III) at the SnO₂/NaCl solution interface were also investigated. Adsorption was investigated in the pH range of 2 to 10. The zeta potential, surface charge density, adsorption density, pH_50% and ΔpH_10-90% parameters for different concentrations of carrying electrolyte were presented. The adsorption reaction constants involving the surface hydroxyl groups were determined using the numerical optimization method.