A simple diffusion model based on Fick's Law for diffusion was developed to simulate the evaporation/diffusion rate of small volumes of perfume liquid mixtures over time and distance. Thermodynamic UNIFAC model was used to predict the vapor-liquid equilibrium, since fragrance solutions were considered as non-ideal liquid mixtures. The diffusion model was applied to concentrated perfume mixtures but also to quaternary mixtures, considering the existence of a solvent matrix (ethanol). The PTD (R) methodology was applied to the study of the perfume evaporation and interpreted along with evaporation lines (EL) that traced the evaporation path of the perfume mixture. The performance of the perfume mixtures studied in this work was analyzed considering the odor intensity and lastingness of the odorants at different distances from the simulated point of application of the perfume and over time. Perfumery performance parameters, namely impact, tenacity, diffusion and volume, were studied in the light of the diffusion model. The use of fixatives and different base notes in the formulation of the perfume and their role on the performance was studied as well as the impact of the ethanol matrix in fragranced mixtures. (C) 2009 Elsevier Ltd. All rights reserved.