We perform a molecular dynamics simulation for CO2 + ketone mixtures to study the molecular motility and elucidate how CO2 molecules are dissolved in a mixture. The self-diffusion coefficients increase with increasing CO2 mole fraction (x(co2)) and decreased with increasing molecular weight. These results mean that the mobility of molecules depends on the molecular size. To study molecular aggregation around CO2 molecules, radial distribution functions (RDFs) and the distance from neighboring molecules to CO2 molecules were calculated. The RDFs indicate that the CO2 molecule exists near the carbonyl oxygen atom. Because of the distance of the neighboring molecule from the CO2 molecule, the CO2 molecule is less likely to exist around a branched alkyl ketone than a normal alkyl ketone. (C) 2010 Elsevier B.V. All rights reserved.