This study presents the first data of Po-210 and Pb-210 activity concentrations using moss species Hypnum cupressiforme from Thrace region, the northwestern part of Turkey. The moss samples were systematically collected from 40 locations in the study area. The average with standard deviation and range of Po-210 and Pb-210 activity concentrations were found to be 409 +/- 128, 188-777 and 494 +/- 183, 178-852 Bq kg(-1) at dry weight, respectively. Comparatively higher radionuclide activities were found in the northeastern Thrace, probably due to Rn-222 daughters attached to aerosols through high rainfall in this part of the region. A significant positive correlation was found between Po-210 and Pb-210, which shows that their source and/or bioaccumulation behavior are similar. The average and range of Po-210/Pb-210 ratio were calculated to be 0.89 and 0.47-2.67, respectively. Those levels were calculated to be mostly lower than unity that addressed the abundance of Pb-210, probably due to predominantly inorganic particles through atmospheric deposition.