Mixed oxides obtained by thermal decomposition of layered double hydroxides have been studied in the reaction of hydrocarbon steam reforming for producing hydrogen. The introduction of several elements on the structure could influence the metal electronic configuration, reducibility, particle size, dispersion and surface area modifying its catalytic performance. The effect of composition on structure and reactivity of these materials has been studied. Nickel, magnesium and aluminium from base catalyst have been substituted by different elements. Ni has been substituted by other active metals for this process like Co, Cu, Pd or Ru; Mg has been substituted by Mn, Zn, Ca or Li; and Al has been substituted by Fe, Cr, La or Ce. Samples have been characterized by N-2 adsorption (BET), X-ray diffraction (XRD), temperature-programmed reduction (TPR) and elemental analysis. Composition has an important effect on catalytic performance. (c) 2007 Elsevier B.V. All rights reserved.