A novel method to determine the widths of the distributions of implanted atoms and of atomic defects from resistivity measurements is described for implantation of H, D, and He in thin films of Au and W at 5 K and energies from 0·25 to 3 keV. The widths obtained for He in W are in agreement with experimental data from field ion microscopy but deviate from results of Monte Carlo simulations (“TRIM”-code). Furthermore the resistivity contribution per implanted atom are derived, giving ρH. D= 1.7 ± 0.5 and ρHe= 3.3 ± 0.8 μΩ/u.c. in gold and ρH.D= 1.6 ± 0.2 and ρHe= 7.6 ± 0.6 μωm/u.c. in tungsten. The number of defects produced per implanted ion are determined from resistivity damage rate measurements. Calculations shows that the threhold energy for atomic displacement and the displacement function under low energy light ion irradiation agree reasonably with respective values derived from electron irradiation.