This study was performed in one of the most important parks of Turkey, the Hatila national park, where a gold mining activity is planned to be conducted. For this purpose, 40 moss samples were collected for heavy metal and radioactivity measurements. A radioisotope excited Xray fluorescence analysis using the method of multiple standard additions was applied for the elemental analysis of mosses collected in Hatila valley national park in the Eastern Black Sea region of Turkey. An annular 50 mCi Am-241 radioactive source and annular 50 mCi Fe-55 radioactive sources were used for excitation of characteristic K-X rays. An Si(Li) detector which had a 147eV full width at half maximum for 5.9 keV photons was used for intensity measurements. A qualitative analysis of spectral peaks showed that the samples contained potassium, calcium, titanium, iron, tin and barium with average concentrations of 230, 5340, 450, 70, 4 and 33 mg.kg(-1), respectively. Cs-137 and K-40 using gamma-ray spectroscopy were determined in 40 moss species collected from the Hatila valley national park. Average activity concentrations of K-40 and Cs-137 were found to be 103 and 272 Bq.kg(-1), respectively. As the region was shown to be heavily contaminated by the Chernobyl accident, the high concentration of Cs-137 could be due to this accident. The results are compared with those obtained in different parts of the world where gold mining activities are being conducted. The possible consequences of these results are briefly discussed from the point of potential hazards to ecology and human health.