The behavior of zirconia supported Ru and/or Pt catalysts in conditions of TPReduction and pulse chemisorption is studied. In order to understand the process of precursor decomposition, several catalysts prepared by either (co)adsorption or (co)impregnation methods and treated in air or nitrogen are investigated by DSC, MS, and by IRS. A possible adsorption path of Ru(NO)(NO3)(3) over zirconia and its subsequent decomposition during catalyst conditioning is discussed. Stabilization of supported ruthenium in the presence of platinum due to formation of bimetallic cluster was observed, especially when the catalyst was prepared by adsorption.