In order to obtain more detailed information about supported metallocene/methylaluminoxane catalysts, 2 catalysts are supported onto a flat silicon wafer by spin-coating impregnation. These model catalysts are characterized by SEM and EDX showing a film of metallocene catalyst dispersed inside the methylaluminoxane matrix, as well as regions of a localized increased concn. of the catalyst. Applying these model catalysts in a gas-phase polymn. reactor results in rather homogeneous films of polyethylene and polypropylene, resp. In addn., crater-like and spherical polymer structures can be obsd., probably formed by inhomogeneous catalyst distribution.