The concentrations of ¹³⁷Cs and potassium in the surface layers of arable soils were analyzed in the selected region of Eastern Poland approximately 20 years after the Chernobyl power plant accident. Additionally, the occurrence of the elements in soil in the forms available for plants was determined. In relation to the total concentrations of ¹³⁷Cs and ⁴⁰K in the soil, cesium is found in larger quantities in the forms available for plants than potassium. Radiation doses through ingestion were estimated on the basis of ¹³⁷Cs and ⁴⁰K measurements in food samples. It was proved that during the period 1998-2007 the annual average intake of radiocesium per person exceeded twofold the national average, whereas the intake of potassium satisfied the body’s daily demand for this element.