Among the possible remedial actions to reduce the soil-to-plant transfer of radiocaesium and radiostrontium, the addition of clay minerals or zeolites aims at increasing permanently the radionuclide fraction adsorbed on the solid phase, thus lowering the radionuclide solution level available for root uptake. The traditional procedure to test the effectiveness of such amendments is rather empirical: the amendments are applied to the soil and the effect is expressed in terms of the change of the transfer factor, defined as the ratio of Bq per kilogram plant and soil. This procedure yields no insight in the processes responsible for the observed effect and does not allow predictions for other scenarios. Based on the knowledge that soil-to-plant transfer essentially depends on soil type, the use of soil amendments was investigated by quantitatively addressing the physico-chemical parameters which govern solid/liquid partitioning of radionuclides in soils and soil amendments. It is shown that this approach allows to identify the potential soil/amendment combinations to estimate the effects to be expected.