High concentration of radon in the premises leads to a risk of oncological diseases in the population living on the lower floors of buildings. In this regard, an assessment of the potential hazard of radon is made in the construction sites under the production of design and construction works. In the Russian Federation radon flux density measured on the earth's surface is used to estimate the potential radon hazard of the building site. The research of the relationship between the radon flux density values and the amount of radium in the soil from which radon is formed is topic of interest. The article demonstrates the comparative analysis of the measuring results of radon flux density and specific activity of Ra-226 obtained on the surface of the different soil types. EXPERIMENTAL PART Radon flux density measurements were carried out in the spring-summer period of 2018 at three testing sites in Tomsk (terrace of the Tom River in the Lagerny Garden, Russia) and seven sites of Gorny Altai (Russia), characterized by different types of soil.