Al2O3 was modified with TiO2 and ZrO2 using organometallic precursors and is used in the preparation of supported platinum catalysts. The catalysts have been characterised by nitrogen adsorption, hydrogen chemisorption and X-ray diffraction and were tested for their activity in the hydrodechlorination of chlorobenzene. The investigations show that support modification controls the catalyst deactivation remarkably and the catalysts were found to be highly active and selective.