Hydrodistillation of essential oils from leaves of myrtle, rosemary, and sour orange was experimentally studied and the extraction process was modeled. A mass balance was carried out over an assumed flat leave particle and the use of Fick's second law of diffusion led to the mass transfer equation. Its resolution required adequate boundary and initial conditions. The model considered the effect of the main processing parameters on the overall essential oil extraction efficiency as well as the determination of the optimum conditions. To assess the reliability of the model, yield curves for all studied conditions and variation of the oil composition with time were compared with the experimentally obtained results for each plant leave. The agreement seems to be reasonable, although some refining of the model is necessary by taking into account both the diffusion and reaction contributions.