This work presents a study of natural radioactivity levels in coal and its combustion residues (fly ash and slag) used in the houses in Black Sea Region, Turkey. Coal, fly ash and slag samples were provided from different locations of the region and analyzed by gamma spectroscopy using a high-purity germanium detector (HPGe). Also, chemical analyses of these samples were carried out using energy dispersive x-ray fluorescence spectrometer. The mean Ra-226 activity concentrations in coal, slag and fly ash were measured as 83, 99 and 38 Bq kg(-1), respectively. The mean Th-232 activity concentrations in coal, slag and fly ash were measured as 108, 113 and 50 Bq kg(-1), respectively. The mean K-40 activity concentrations in coal, slag and fly ash were found to be 366, 381 and 204 Bq kg(-1), respectively. The potential radiological hazards associated to these materials were evaluated by calculating the radium equivalent activity (Ra-eq), the air absorbed gamma dose rate (D), the annual effective dose rate (AED), the external hazard index (H-ex) and internal hazard index (H-in) and compared with the internationally, accepted or reference values. The mean Ra-eq values of the coal, fly ash and slag samples were lower than the recommended maximum values 370 Bq kg(-1) by the Organization for Economic Cooperation and Development (OECD). The overall mean outdoor terrestrial gamma air absorbed dose rate in coal, fly ash and slag samples are 119, 129 and 62 nGy h(-1) and the corresponding outdoor annual effective doses are 0.60, 0.32 and 0.64 mSv y(-1), which is higher than the worldwide average (0.07 mSv y(-1)), respectively. Moreover, the enrichment factors relative to the input coal are calculated for the radionuclide contents observed. Calculated enrichment factor values for Ra-226 and Th-232 were found 1.14 and 1.01, respectively.