Information about the sorption of radionuclides on natural materials used for cementation of liquid radioactive wastes (RAW) is important for predictions of migration rates of radionuclides in the products of fixation. Cementation process for conditioning liquid RAW uses, besides cement, materials which improve quality of products. In Czechoslovakia technology among these materials are clinoptilolite tuffit, mordenite tuff, tobermorite and fly ash. Liquid RAW issued from nuclear power plants contains the principal radionuclides60Co,134Cs and137Cs, therefore, a sorption study of these radionuclides was carried out. pH of liquid RAW was 12.5–13.7 and salt content ca. 200 g·dm–3. Results of sorption are given by distribution coefficients. The best results for cesium in those pH region and salt content had mordenite tuff DCs=100 dm3·kg–1 and the worst results had fly ash DCs=4.1 dm3·kg–1. The best results for cobalt in those solutions had tobermorite DCo=38 dm3·kg–1 and the worst results had fly ash DCo=6.9 dm3·kg–1.