This paper presents the results of measurements of natural radioactivity of K-40, Ra-226 and Th-232 in building materials as well as radon concentrations and dose rates in houses and outdoors. The mean absorbed rate in air outdoors from natural gamma radiation was found to be 40.2 nGy/h^-1. Doses inside houses made from particular materials were (nGy/h^-1): brick - 102, prefabricate - 89, wood - 88. The mean equivalent concentration of radon indoors was 12 Bq/m^-3. The calculated annual effective dose equivalent per one statistical inhabitant of "Poland Green Lungs" is 1.61 mSv/year. The doses absorbed by the population in the northeastern region of Poland from natural sources of ionizing radiation are lower than the population-weighted world averages.