Solvent Free Microwave Extraction (SFME) has been used to obtain essential oils with similar quality and yield to those obtained using conventional steam distillation, but using less energy and processing time. In this work, mass transfer of essential oil from plant surface to the steam phase during SFME is studied. Based on experimental evidence, a process model is proposed, relating water evaporation rate with fluxes of the main components of Lavandin super (linalool and linalyl acetate). Data showing differences in mechanism of extraction between steam distillation and SFME are also presented.