The reduction of acetophenone catalysed by Ru(diphosphine)(diamine) complexes, with various diphosphine and diamine ligands, has been investigated theoretically using density functional theory. The results show a correlation between differences in the calculated activation energy (Delta E-a) and enantiomeric excess (ee) in ruthenium-based asymmetric hydrogenation catalysts, suggesting that computational procedures may be able to predict the effect on the ee of ligand substitutions.