A theoretical study of hydrogen deposition and insertion in bimetallic Pd-Pt nanoalloys has been carried out in the framework of the density functional theory. Our model systems are 147-atom clusters of cuboctahedral shape and stoichiometries of Pd 1.00, Pd 0.91Pt 0.09, Pd 0.82Pt 0.18, and Pd 0.54Pt 0.46, resembling those recently produced and characterized in the context of H insertion (Kobayashi, H. et al. J. Am. Chem. Soc.2010, 132, 5576.). Adsorption and absorption energies have been computed for H in all stable positions for the different compositions. Absorption is found to improve for nanoalloys with a small Pt concentration of 8-20%. However, when the Pt content approaches 50%, the absorption capability worsens, even as compared with the pure Pd nanoparticles. These trends are fully consistent with the experimental data. The local geometrical and electronic environments of hydrogen in these alloy nanoparticles are explored in detail so as to understand the observed behavior. Concerning the H deposition, our results indicate that Pd-Pt nanoalloys with high Pt content might be efficient in regard to preferential oxidation reaction mediated by hydrogen. © 2011 American Chemical Society.