Tracer diffusivities, D-12, of eucalyptol in liquid ethanol and in supercritical carbon dioxide (SC-CO2) mixed with ethanol (8.0 wt.%) were measured in the temperature range 303.15-333.15 K, using the chromatographic peak broadening technique. The obtained diffusivities ranged from 0.912 x 10(-5) to 1.578 x 10(-5) cm(2)s(-1) for the binary system (pressure range 1-100 bar) and from 0.547 x 10(-4) to 1.042 x 10(-4) cm(2)s(-1) for the ternary system (pressure range 150-275 bar). The dependence of D-12 on temperature, pressure, solvent density, and Strokes-Einstein coordinates were deeply examined. Such trends were interpreted and discussed in terms of free volume theories and hydrodynamic fundamentals. Various prediction/correlation models were assessed to calculate D-12, with the best results (deviations of 1.20-7.00%) obtained with Dymond-Hildebrand-Batschinski equation, the Tracer Liu-Silva-Macedo (TLSMd) model, four correlations of Magalhaes et al., and a modified Stokes-Einstein equation. Lai-Tan and Wilke-Chang correlations attained reliable results (errors of 8.36 and 8.00%) in the case of eucalyptol/SC-CO2/ethanol system.