Deposition of tin-oxygen species on mesoporous silica (MCM-41) was achieved via chemical reaction of SnEt 4 vapour with surface silanol groups followed by heat treatment in air. Evidence suggested that highly reactive tin-oxygen overlayers were formed on the internal surface of the MCM-41 silica. These tin-oxygen modified silicas, after H 2 pre-treatment, showed excellent activity in catalysing reduction of crotonaldehyde to crotyl alcohol using propan-2-ol as the hydrogen transfer agent (acetone was formed as the by-product). It was also found that the catalytic activity per gram of tin increased dramatically as the tin loading decreased. The increase in the specific activity with the decrease in tin loading was attributed to the improved dispersion of the tin-oxygen overlayers.