Adsorption of the gadolinium from H ₂ O and HCl solutions on the ion-exchange resin C100 is investigated. The experiments were carried out by varying the acidity of the liquid phase, the amount of sorbent, and the temperature. The maximal sorption of the ions Gd ³⁺ is observed from the solution 0–0.2 M HCl under optimal conditions, the sorption reaches more than 99.5%. Sorption of Gd ³⁺ on C100 from H ₂ O solution occurs most intensively during the first 3 min then for 30 min the system smoothly comes to equilibrium. The maximal sorption capacity of the resin C100 amounted to 1.2 ± 0.1 mmol g ⁻¹ . The thermodynamic parameters of sorption: ΔG = − 24.20 kJ mol ⁻¹ , ΔS = − 90.27 J mol ⁻¹  K ⁻¹ , ∆H = − 50.93 kJ mol ⁻¹ were evaluated. It is shown that the sorption of gadolinium on the ion-exchange resin C100 is described by models of kinetically pseudo-first and pseudo-second order. It is established that the Gd ³⁺ sorption on the C100 resin is reversible second order chemical reaction.