Regulation of persistent organic pollutant (POP) emissions and reliable monitoring of POP concentrations in ambient air is of paramount importance because of their slow rates of degradation, toxicity and potential for long-range transport and bioaccumulation in living organisms (Aarhus protocol, 1998). Polycyclic aromatic hydrocarbons (PAHs) in particular are ubiquitous and appear to be carcinogenic, mutagenic and immunotoxic. Their concentrations in mosses have shown similar spatial patterns and temporal trends to ambient air concentrations (Holoubek et al., 2007). This study was carried out to investigate whether mosses can be used as biomonitors of atmospheric deposition of PAHs at a European scale. Mosses Hypnum cupressiforme Hedw. were collected during October 2010 in 3 regions of Europe: Île-de-France (France), Navarra (Spain) and the Swiss Plateau (Switzerland). PAH concentrations were determined by High- Performance Liquid Chromatography (HPLC) associated with fluorimetric detection. Stable isotopes at natural abundance levels in mosses also provide a powerful approach for understanding environmental interactions. Isotopic composition of elements, such as carbon and nitrogen, changes in predictable ways during their course through the biosphere, which makes them ideal tracers of the pathways and origins of these elements (Liu et al., 2008). C and N content were determined by an elemental analyzer and stable isotopic ratios 13C and 15N with an isotope ratio mass spectrometer operating in continuous flow mode. Spatial trends of PAH concentrations, C & N contents and 13C & 15N isotopic ratios were plotted and treated statistically with heavy metal concentrations obtained during the 2010 ICP-Vegetation survey, as well as emission values (EPER), soil occupation (Corine Land cover), geomorphological and meterological data.