Epoxidation of 2-cyclohexen-1-ol with TBHP and TiO2-SiO2, Fe2O3-SiO2 and SiO2 aerogels has been studied. The influence of surface silanol groups and transition metal impurities in titania-silica on the product distribution has been analyzed. The results, supported by literature data, indicate that high surface area silica cannot generally be regarded as an inert matrix in epoxidation catalysts, Contribution of Ti-free silica limits the selectivity of Ti- and Si-containing catalysts in demanding epoxidation reactions. The activity of silica -together with the background oxidation of the olefin - may lead to overestimated intrinsic activities when the reaction rate is related to the Ti content of the catalyst.