Proton implantation into Pd has been performed to examine the effects of defects in a subsurface region on the hydrogen storage of the material. Positron annihilation measurements using monoenergetic positrons indicated the formation of vacancy-type defects in a proton implanted region of Pd. The absorption rate of hydrogen was found to decrease by the introduction of defects in Pd due to implantation whereas the total amount of hydrogen absorbed in proton implanted Pd was almost the same as that in unimplanted. one. Based on these results, the correlation between the defect formation and the hydrogen absorption is discussed.