Three olefin polymerization catalysts are supported onto a flat silica wafer employing spin-coating impregnation. These model catalysts feature a defined surface direction of the silica support and thus facilitate the direct correlation between catalyst dispersion and morphology of the polymer product. Depending on the interaction of the catalysts with the silica surface, the catalysts disperse in very different fashions, which induces different constraints on the polymer growth upon gas-phase polymerization. Chemical anchoring of the active species as in the CrOx/SiO2 (Phillips) system results in homogeneous polymer film of up to several 10 mum. In contrast the physisorbed Cp[1,3-(2,6-Me2C6H3)(2)C2H4N2C=N]-TiBz(2)B(C6F5)(3) forms clusters on the flat silica that evolve into highly porous, ball-shaped polymer beads. rac-[Me2Si(2-Me-4-(1-Naph)Ind)(2)]ZrCl2(CH3AlO)(x) forms a film of metallocene catalyst dispersed inside the cocatalyst matrix. Homogeneous regions of this film give rather homogeneous polymer films while local concentrations of active species (hotspots) form crater- and ball-shaped structures.