Clearly discernible rings of high photocatalytic activity, i.e. rings of activation, RoAs, are formed around Pt macro-sized (radius: ro 1 mm radius) Pt islands, i.e. Pt ‘dots’, deposited on TiO2 films, which have been covered with a visible pollutant, such as soot, or a dye, such as acid orange 7, AO7. The features of the RoA region appear very similar for soot or dye-covered films. Thus, the radius of the RoA region, ra, appears to depend weakly, if at all, on ro, and is typically 0.60-0.68 mm > ro. The rate of photocatalytic removal of the surface pollutant inside the RoA is uniform and significantly greater, i.e. ca. 3.2 - 5 x's, than that outside the RoA region. RoA region formation is observed for: (i) Pt dots which have been photodeposited or created through thermal reduction, (ii) Pt dots on sol-gel and commercial (paints and tiles) TiO2 films and (iii) Pd dots, but less clearly for Au dots. A simple mechanistic rationale for RoA region formation is presented and the potential importance of this feature, with regard to improving the performance of commercial photocatalytic films, is discussed briefly.