In small-plot field trials in two localities, we explored the effect of various doses of selenium in the form of sodium selenite in the soil (0, 12, 24, 48 and 72 kg Se per hectare) on its concentration in potato tubers of two varieties. The results showed that the Se content in the tubers increased with the applied dose from 0.20 to 4.88 mg Se per kg of dry matter and from 0.034 to 0.829 mg Se per kg of green matter. No statistical differences in the Se concentration in the tubers between the varieties were detected. The effect of the locality was relevant; the average Se content in the tubers was different (2.59 and in 1.77 mg Se per kg of dry matter). Application of an optimal dose of Se into the soil before potato planting increased the Se content in the plants thus ensuring the input of necessary amounts of this essential element into the food chain.