Crystal structures of ivanyukite-Na-C, ivanyukite-K, Th-analogue of ivanyukite-K and Cs-substituted ivanyukite-K have been solved. Removing of sodium cations from initial ivanyukite-Na-T is accompanied by moving of K cations to the channel axes and the framework transformation into the cubic symmetry. Cations of Th and Cs also occupy the channel axis without the framework distortion. Results obtained have confirmed a cation-exchange mechanism of Cs and Th sorption on the ivanyukite-group minerals and perspectives of using the synthetic analogue of ivanyukite for the radioactive waste treatment.