This work investigates extraction of p-carotene by supercritical carbon dioxide and nitrous oxide from impregnated beds and from freeze-dried carrots. Extraction rate was measured as a function of temperature, flow rate and particle size. Based on results from spiked beds, mathematical models were proposed to analyze the dynamic behavior of extraction from carrots. The validity of a diffusion model or a mass balance model was discussed through results on particle size. Although the diffusion model and the experimental results were in good agreement, provided that two stages of diffusion were considered for larger particle size, we further analyzed all data regarding a differential mass balance model. This model, accounting for external mass transfer, diffusion within the matrix and dissolution at the solid/fluid interface, described the time-dependent process satisfactorily despite assumptions on the matrix description. Results showed that both external mass transfer and desorption of solute from the matrix were the limiting steps.