At 31 sites in Finland ³²S and ³⁴S isotope composition of the terrestrial lichens were determined of the epiphytes Hypogymnia physodes (L.) Nyl. growing on pine and birch, and Pseudevernia furfuracea (L.) Zopf on pine, terricolous lichen Cladina spp., and pine bark. A highly significant negative correlation of the δ³⁴S values in relation to S contents of Hypogymnia physodes revealed clearly elevated δ³⁴S values in the oxidation zone of sulphide ores. Iron of the other epiphyte P. furfuracea on pine was associated with S in sulphide form leading to higher δ³⁴S values. The δ³⁴S values of the terricolous lichen Cladina spp. had no correlation with its S contents, but the δ³⁴S values correlated highly significantly with Fe. The interspecies differences of the δ³⁴S values in the studied lichens were clearly distinguishable.