Mass-transfer efficiencies and hydraulic characteristics of a 3.18-cm spray and a packed column for extracting ethanol from aqueous ethanol solution with supercritical carbon dioxide were investigated. Experiments were performed at 308.2, 313.2, and 323.2 K over a pressure range from 9.1 to 12.2 MPa. The influences of fluid properties, phase flow rates, column internals, and phase dispersion on mass-transfer efficiencies and hydraulic characteristics are discussed. An extension of a model for predicting mass-transfer efficiency in conventional liquid-liquid extraction to supercritical-fluid extraction was attempted. The model for mass-transfer efficiencies, developed for conventional spray and packed liquid-liquid extraction columns, was in good agreement with our experimental results.