The interaction between hydrogen and defects in annealed,473K tempered and cold-rolled nickel samples has been investigated by positron lifetime and Doppler broadening measurements.Experimental results show that there has been no effect of hydrogen-charging on the nickel samples containing only dislocations,while in the samples containing vacancies the effect was evident.A long-lifetime component appeared for the latter,which may indicate that the hydrogen-vacancy composite is also the center of vacancy agglomeration.