Chemical composition of the essential oils obtained by hydro-distillation from Artemisia annua L. (Asteraceae) harvested before flowering (BF), 50% of flowering (50%F), full flowering (FF), and after flowering (AF) stages were determined using GC and GC/MS analysis. The essential oil contents were 0.8%, 0.96%, 1.22% and 1.38% in BF, 50% F, FF and AF, respectively. In total, 20 compounds were identified, with artemisia ketone (28.30%-37.15%), camphor (18.00%-23.30%), and 1,8-cineole (9.00%-10.39%) as main components. The highest amounts of the three main components were recorded in the essential oils of the plants harvested in the FF stage. Also, the free radicals scavenging activity of the essential oils, tested by using DPPH method, were found to be in order of FF>50% F>AF>BF.