The influence of the crystalline structure of ZrO2 on the metallic properties of Pt, when supported on WO3-ZrO2, was studied. Pt supported on tetragonal zirconia loses its metallic properties while when supported on monoclinic zirconia it presents good metallic activities. WO42- deposited on amorphous Zr(OH)(4) before calcination generates an active material for n-butane isomerization. The larger the fraction of the tetragonal phase of zirconia in this material, the higher the isomerization activity and the lower the metallic activity of Pt.