Catalyst samples containing nanosized Pt, Ni, Fe, or Zn powder were prepared on the basis of high-silica zeolite ZSM-5 by mechanical mixing. The structure and state of active centers of zeolite catalysts (freshly prepared or calcined after the reaction cycle of upgrading the petroleum straight-run gasoline fraction) were studied by means of the X-ray diffraction, UV spectroscopy, and X-ray photoelectron spectroscopy techniques. It was shown that the oxidized forms of the metals are practically absent from the freshly prepared zeolite samples. After the heat treatment of the catalysts in air, nanosized metal powders transform into oxides on the zeolite surface, with iron and nickel producing the greatest variety of oxidized forms.