An improved hydro-isomerization catalyst composed of platinum and/or palladium distended as very small crystallites on a hydrogen form mordenite base is disclosed. The catalyst is prepared by distending the noble metal on the base by addition of small quantities of cerium nitrate in admixture with the noble metal followed by controlled calcination to achieve an almost monatomic dispersion of the noble metal on the base. The catalyst thus prepared is used to isomerize normal paraffins in the C4 to C7 range in the presence of hydrogen at elevated temperature and pressure.