Essential oils from aerial parts of several Artemisia arborescens L. populations, collected in five different localities of Sicily were analyzed by GC-FID and GC-MS in order to study the chemical composition and its variability due to phenological stage. Forty-three compounds, accounting for more than 92% of the oil, were identified. Monoterpene fraction with the exception of Petru population was higher than the sesquiterpene fraction. beta-thujone (20.5-55.8 %), chamazulene (15.2-49.4%), camphor (1.3-10.7%) and germacrene D (2.3-3.4%) were the main compounds. Chemical composition was influenced by phenological stage, with an increase in the monoterpene fraction at flowering stage; in both stages, the main compounds were always the oxygenated monoterpene beta-thujone and the sesquiterpene hydrocarbon chamazulene.