In this thesis the deposition of persistant organic pollutants, specifically polycyclic aromatic hydrocarbons (PAH) is analysed in the moss species Hypnum cupressiforme Hedw. PAHs pose a threat to human health and the environment, therefore many of them are listed in many countries as substances that have tobe controlled and reduced. Samples were collected at fifteen plots in the forest environmet across Slovenia. Gas chromatography with mass spectrometry was used to determine the concetrations of PAHs in mosses. The highest avarage concentration was found for phenanthrene, fluoranthene, pyrene and naphthalene, which are present in the atmosphere due to traffic emissions and fossil fuel incineration. Higher concentrations were measured in six plots in relative proximity to urban centers, roads and tourist sites. Concentrations of low molecular PAH dominate. In comparison with some other European countries, low PAH concentrations in mosses in Slovenia are found.