Bifunctional Pt/H-beta and Pt/H-MOR catalysts were prepared under various pretreatment conditions and applied to the isomerization of n-hexane. Pt/H-beta gave rise to the higher yield of high octane dimethylbutanes than the commercial Pt/H-MOR. To explain this result, both the dispersion and distribution of Pt clusters in the zeolite channels were investigated. The acidity and the distribution of acid sites in both catalysts were also examined by using ammonia and pyridine as probe molecules. Pt/H-beta was found to be a potential catalyst for the isomerization of il-hexane because Pt clusters could be well dispersed to give proper balance between metallic centers and acid sites in H-beta zeolite although its acidity was low compared with H-MOR.