Uranium mine Žirovski vrh in Slovenia was closed in the year 1993. In the past years a lot of work was done for restoration of the area around the mine. There are two tailing sites, Jazbec and Boršt, filled with material with high specific activity of 226Ra. Tailings are covered by different layers of clay and soil in depth of 2 m for reducing radon exhalation rate. Gras, growing on the surface of tailing sites has been used as fodder for domestic animals. We were interesting about the amount of the specific activity of natural radionuclides 238U, 226Ra or 210Pb, transferred from the covering soil on the tailing to the grass on the surface area. The transfer factors of naturally occurring radionuclides have not been studied to the same extent as their artificial counterparts, but some comprehensive investigations have been done by various institutions around the world. In case of 226Ra calculated values are two times or four times bigger than measured. For 210Pb measured values are up to hundred times bigger than calculated. The reason for that is radon in the air, decays to the 210Pb, deposited on the grass and not 210Pb coming from the soil.