A series of hybrid supported catalysts were prepared by combining (iBuCp)(2)ZrCl2 and {Tp(Ms)*} TiCl3 complex (Tp(Ms)* = HB(3-mesityl-pyrazolyl)(2)(5-mesityl-pyrazolyl)(-)) sequentially grafted onto MAO (methylaluminoxane)-modified silica according to a Plackett Burmann 2 3 design. Supported catalysts were prepared taking into account the immobilization order, silica pretreatment temperature, and grafting temperature. Grafted metal content was comparatively determined by Rutherford backscattering spectrometry (RBS), X-ray photoelectronic spectroscopy (XPS), and inductively coupled plasma-optical emission spectroscopy (ICP-OES). The resulting catalysts were evaluated in terms of catalyst activity and polymer properties. According to RBS measurements, grafted metal content remained comprised between 0.1 and 0.5 wt % Zr/SiO2 and 0.1 and 0.3 wt % Ti/SiO2 depending on the immobilization order and on silica pretreatment temperature. All the systems were shown to be active in ethylene polymerization having external MAO as cocatalyst. Catalyst activity seemed to be governed by the zirconocene species, influenced slightly by Ti ones. Resulting polymers were characterized by DSC and GPC. The polyethylenes mostly presented higher molecular weight than those produced by homogeneous catalysts or by zirconocene grafted on bare or on MAO-modified silica.