The hydroisomerization of n-heptane to dibranched and tri-branched products for producing high octane gasoline has been studied using unidirectional 12 Membered Ring (MR) zeolites with different pore diameters, and zeolites with other pore topologies including one with connected 12 x 10 MR pores and two tridirectional 12 MR zeolites. Besides the pore topology, the crystallite size of the zeolite was seen to be of paramount importance for improving activity and selectivity. In a second part of the work, a Light Straight Run naphtha including n-pentane and n-hexane and another feed containing n-pentane, n-hexane, and n-heptane have been successfully isomerized using a nanocrystalline Beta (BEA) zeolite. This can be a favourable alternative to the commercial zeolite catalyst based on mordenite (MOR), especially when n-heptane is present in the feed.