Different values are obtained for dangling-bond (DB) densities evaluated by electron spin resonance (ESR) and the constant photocurrent method (CPM) in undoped and N-doped hydrogenated amorphous silicon (a-Si:H) films with various thicknesses during light-soakings using white light and red light. The origin of the difference was analyzed by taking into account the inhomogeneous distribution of photocreated DBs across the film thickness caused by the penetration depth of the light being less than the film thickness. The main cause of the difference in undoped a-Si:H was found to be the inhomogeneous distribution of photocreated DBs, whereas the main cause in N-doped a-Si:H was found to be the presence of a large amount of negatively charged DBs inactive to ESR. The presence of the thin near-surface layer with a high density of DBs blind to CPM also contributes to the difference between ESR and CPM DB densities both in undoped and N-doped a-Si:H.