Natural radioactivity is one of the essential components of the environment. Unlike the Sudety mountains area in Poland, the Tatra Mountains were not the subject of wide survey as regards the levels of natural radioactivity. Especially, the concentrations of radon (natural radioactive gas) have not been investigated there in terms of their possible negative health impact. Within the frame of bilateral cooperation between the Institute of Nuclear Physics in Kraków, Poland, and the Jožef Stefan Institute in Ljubljana, Slovenia, the measurements of natural radioactive elements in old uranium mines in the Tatra National Park were performed in June 2010. The investigated sites were located in Dolina Białego (The Valley of the White). One of the mines is situated near the tourist path. The paper presents the results of complex measurements of natural radioactivity in both uranium drifts. The concentration of radon gas inside the mining drifts exceeded 28,000 Bq m(-3). Also, very high gamma dose rates were observed (up to 5600 nSv h(-1)). The maximum concentrations of natural radioactive elements (potassium (40)K, radium (226)Ra, thorium (232)Th) in rock samples amounted to 535, 2137, and 18 Bq kg(-1), respectively. The effective dose rates due to radon and thoron inhalation have been assessed as 0.013 mSv h(-1) (for the lowest concentration) and 0.121 mSv h(-1) (for the highest concentration).