Distributions of hydrogen isotope concentrations in ε-phase zirconium hydrides and deuterides (ε-ZrHx and ε-ZrDx: 1.8 < x < 2.0) were investigated by neutron radiography (NRG). The NRG images of the thermal neutron transmission and backscattering revealed hydrogen concentration dependence and isotope differences. The thermal neutron mass attenuation coefficients in relation to the hydrogen isotope concentrations were determined from the transmission NRG images. The results showed the isotope effects of the thermal neutron mass attenuation coefficients for ε-ZrHx to be about 6-9 times higher than those for ε-ZrDx. The neutron scattering processes for transmission and backscattering NRG images of ε-ZrHx and ε-ZrDx were also analyzed using a general Monte Carlo neutron-particle transport (MCNP) code.