Molecular dynamics (MD) simulations were employed to compute tracer diffusion coefficients (D-12) of propanone, butanone, 2-pentanone and 3-pentanone in supercritical CO2, which are in quite good agreement with experimental data available in the literature. It was confirmed that D-12 is enhanced by pressure decrease, temperature increase, and solute size reduction. The radial distribution functions, spatial distribution functions, and coordination numbers derived from the simulations were further employed to understand how molecular structure specificities affect D-12. The simulations proved that the molecular structuring of the solvent around the solute is similar for all ketones, which implies their diffusivities are essentially affected by their size and volume and, to a less extent, by the position of the carbonyl group in the carbon chain. The good agreement between calculated and measured data validates the MD simulations as a cheap and fast alternative to predict D-12 values of ketones in supercritical CO2. (C) 2015 Elsevier B.V. All rights reserved.