Abstract Rosemary oil may be isolated by three different processes, including steam distillation, water distillation and controlled instantaneous decompression. The concrete resulting from extraction by volatile organic solvents was also made using hexane, dichloromethane and ethanol. The oils and extracts obtained were analyzed by gas chromatography (GC) and gas chromatography coupled to mass spectroscopy (GC/MS) in order to determine their chemical composition. A scanning electron microscope was used to observe the impact of different processes on the structure of leaves and essential oil bearing trichomes.