The catalytic oxidation of carbon particles is an important process, e.g., in regeneration of diesel particulate filters. If the catalyst and the carbon particles are not in direct contact, a transportation step of the activated oxygen atoms (oxygen spillover) is needed. The distance of oxygen spillover in a nanoparticle layer system was studied. The system consisted of a platinum catalyst (20 mu m thick) and a carbon (300 mu m thick) layer that were separated by an inert SiO2 layer with variable thickness. At moderate conversion (< 40%), which occurs without substantial structural changes of the carbon particle layer, a distance of 160 mu m was found. The spillover distance of the oxidizing species may be a starting point for the geometric design of more efficient impregnated catalytic particulate filters.