The concentrations of natural radionuclides in 6 differentcolors of volcanic tuff stones which are derived from the Cappadociaregion in Turkey were determined using gamma-ray spectroscopy witha HPGe detector, and the mineralogical composition and formula ofstones were determined by an X-ray powder diffractometer. The averageactivity concentrations of 238U, 232Th and 40Kare 50.7, 58.6 and 717.6 Bq.kg–1, which are higher thanthe world averages of 35, 30 and 400 Bq.kg–1, respectively.The radium equivalent activities (Raeq), external hazardindex (Hex), and internal hazard (Hin) associatedwith the natural radionuclides, alpha (Iα) and gammaindices (Iγ) were calculated to assess the radiationhazard of the natural radioactivity in the volcanic tuff stones.The average indoor annual effective dose equivalent is 0.1 mSv.All values of the indoor effective dose are lower than the exemptiondose value of 0.3 mSv. The calculated radium equivalent activityvalues vary from 60.31 Bq.kg–1 to 281.32 Bq.kg–1 witha mean of 189.78 Bq.kg–1. All values of radium equivalentactivity are lower than the world average. The average indoor absorbeddose rate (Din) for volcanic tuff stones, calculatedto be 21.18 nGy.h–1, is lower than the world averageof 84 nGy.h–1.