A series of hybrid supported catalysts was prepared by sequentially grafting Cp 2 ZrCl 2 and (nBuCp) 2 ZrCl 2 (1:3 ratio) onto synthesized xerogel, aerogel and commercial silicas. Supports and catalysts were characterized by Rutherford backscattering spectrometry, energy-dispersive X-ray scanning electron microscopy, atomic force microscopy and nitrogen adsorption. Grafted metal content laid between 0.15 and 0.5 wt.% Zr/SiO 2 . All the systems were shown to be active in ethylene polymerization with methylaluminoxane as the co-catalyst. Catalyst activity and molecular weight were shown to depend on the textural characteristic of the silicas, namely grain size and pore diameter. The highest activity in ethylene polymerization (ca. 5310 kg PE mol Zr -1 h -1 ) was obtained with the supported catalyst using commercial silicas with average particle size around 50 m. Particles with sizes of 80-90 m obtained less activity. Resulting polymers were characterized by gel permeation chromatography and differential scanning calorimetry.