Essential oils from aerial parts of several Artemisia arborescens L. populations, collected in five different localities of Sicily, were analyzed by gas chromatographâflame ionization detector (GCâFID) and GCâmass spectrometry (GCâMS) 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. Î²-Thujone (20.5â55.9%), chamazulene (15.2â49.4%), camphor (1.3â10.7%) and germacrene D (2.3â3.4%) were the main compounds. Chemical composition was influenced by phenological stage, with an increase in the monoterpene fraction at flowering stage; both in flowering and vegetative stages, the main compounds were always the oxygenated monoterpene Î²-thujone and the sesquiterpene hydrocarbon chamazulene.