The chemical content of the lichen species Cetraria islandica has been studied. Concentration of a chloroform-methanolic extract led to the isolation of fractions containing hydrocarbons, fatty alcohols, fatty acids, keto-acids, dicarboxy lic, acids, sterols, mono-, sesqui-, di- and triterpenoids, and some aromatic compounds. The C17-alkadiene, linoleic- and linolenic acid, ketostearic acid. Protolichesterinic acid and fatty acids similar to protolichesterinic acid were found as the main constituents. of the lichen extract. Most of the detected compounds are new for th is lichen species. Our results also revealed some unknown constituents.