This M.Sc. thesis is focused on geochemical position of lithogenic and anthropogenic thallium in forest and agricultural soils. Two localities with different contamination source were chosen for this study. The first studied locality with occurrence of lithogenic thallium only, was an area of Kluky u Písku (South Bohemia). The second studied locality with anthropogenic thallium occurrence was the area of Olkusz (South Poland). The thallium fractionation forms in studied soils were detected by a sequential extraction procedure. The significant differences in thallium distribution and mobilization were observed at both localities. It was found that the erosive and bioturbation processes, as well as dust deposition into the soils, represent the main factors for lithogenic thallium mobilization and thallium distribution between biotic and abiotic components of the environment. Dust deposition of anthropogenic thallium depends mainly on predominant wind direction in landscape, or landform of target area (presence/absence of forest etc.). Ore processing methods and an inappropriate location of disposal sites also played an important role in the mobilization/imobilization process of anthropogenic Tl and soil contamination.