Reactivity of C-4-C-6 olefins during the selective HDS of a full boiling range FCC gasoline over PtPd/USY catalyst was studied under various process conditions. Effect of the structure and carbon number of olefins on their conversion is discussed. it was found that the rate of hydrogenation decreases with the carbon number of linear olefins. Terminal olefins are readily converted to internal ones by double bond shift to approach the equilibrium composition of olefin isomers. (C) 2008 Elsevier B.V. All rights reserved.