Selectively modified mesoporous silica has been infiltrated with Pt nanoparticles by a simple in-situ reduction method. The method is based on functionalizing the inside pore channels with highly reducing Si-m-H bonds, which results in a preferred growth of Pt nanoclusters (about 15 wt.-% on average) along the channels of the mesoporous silica. The Figure shows a TEM image of Pt nanowires aligned along the pore channels of SBA-15.