The equilibrium partitioning and the extent of extraction of a phenolic mixture and a polynuclear aromatic hydrocarbon (PAH) mixture were determined for the three-phase system of soil, water, and supercritical CO2. The effects of temperature and pressure on the partitioning between the phases were investigated. A model was developed to predict the extraction results of mixtures in a three-phase system using two-phase partitioning data. Two-phase experiments (water-CO2 and soil-water) were conducted with both the phenolic mixture and the pure components of the mixture to obtain two-phase partition coefficients used in the prediction model. The extraction results of the PAH mixture were predicted using existing two-phase data for the soil-CO2 system and an octanol-water partitioning correlation for the soil-water partition coefficients. The predictions for both the phenolic mixture and the PAH mixture in the three-phase system of soil-water-CO2 were fairly successful.