This work reports a striking enhancement of catalytic performance of gold nanoparticles (NPs) with average diameter of 3.2 nm partially (ca. 32-40%) confined in the cavity of carbon nanotubes (CNTs) for the gas-phase hydrogenation of 1,3-butadiene (BD), as well as liquid-phase hydrogenation of cinnamaldehyde (CAL). The reaction rates and turnover frequencies of the CNTs confining gold NPs exceed those with a similar size deposited on the outer surface of CNTs and activated carbon by more than one to two orders of magnitude in both two reactions. The selectivity to monobutenes and hydrocinnamaldehyde is up to 100% and 91% at 100% and 95% conversions of BD and CAL, respectively. Au/CNTs catalysts were characterized in depth to establish their structure-property relationship. The peculiar interaction of confined gold NPs with the surface of CNTs facilitates the dissociation/activation of H-2, which is the rate-determining step for hydrogenation reactions demonstrated by kinetic studies. (C) 2012 Elsevier Inc. All rights reserved.