The binary diffusion coefficients of 2-ethyltoluene, 3-ethyltoluene, and 4-ethyltoluene in supercritical carbon dioxide were determined in a pressure range of (15.0 to 35.0) MPa at temperatures of (313, 323, and 333) K by means of the Taylor-Aris dispersion technique. The influence of pressure, temperature, density, and viscosity on the binary diffusion coefficients was examined, and some general trends were established. The experimental results were compared with the values estimated by several semiempirical equations based on the Stokes-Einstein formula and on the Rough-Hard-Sphere model.