The influence of nitrogen implantation on the hydrogen accumulation in Ti, Zr and Hf was investigated depending on nitrogen ion fluence. The samples were implanted with 15N ions in the fluence range from 3 × 10 17 to 9 × 10 17 ions/cm 2. The 15N ion energy, varied between 150 and 220 keV, was chosen to obtain nearly the same projected range in each metal. The concentration depth distributions of the implanted nitrogen and the accumulated hydrogen were quantitatively analysed with the resonant nuclear reaction 15N( 1H,αγ) 12C at 429 keV and by the reverse reaction at 6396 keV, respectively. The hydrogen content is markedly increased in the implanted layer (up to 8 at.%), according to the nitrogen distribution profile. This is attributed to the lattice distortion in titanium, zirconium and hafnium. At a nitrogen concentration above 20 at.%, however, the hydrogen content continuously decreases in the implanted layer due to precipitates of nitrides and thus the hydrogen depth distribution alters its appearance to a saddle-shaped profile. With further increasing nitrogen concentration the two maxima are separated by a plateau with a hydrogen content less than 1 at.%.