Hydroisomerization of BtL-naphtha was investigated over microporous/mesoporous Pt/ZSM-S catalysts. Alkaline and successive acid treatment of microporous ZSM-5 leads to the formation of mesopores (similar to 10 nm). Alkaline treatment removes both Si and Al from the framework, while Si is selectively extracted and Al redeposited on the surface as extra-framework Al, increasing the Lewis acidity and reducing Bronsted sites. Successive acid treatment dissolves alumina deposits, leading to higher surface area and acidity. The mesoporosity was found to improve the selectivity because of the improved diffusivity within the zeolite pores and, as a consequence, the reduced residence time of the intermediates within the pore channels.