Hydrogenation of orthorhombic KHg2-type R(Cu,Ni)2 pseudobinary intermetallic compounds (R = Ce, Pr, Nd) was found to lead to the formation of an orthorhombic insertion-type hydride, which readily transforms into a hexagonal Fe2P-type hydride. This “post-hydrogenation” structural transformation can be accelerated by heating in vacuum at 100-120°C and is accompanied by release of ¼ of the available hydrogen, as has been confirmed by PND studies. Further heating in vacuum leads to disproportionation of the hydride and recombination with recovery of the orthorhombic R(Cu,Ni)2 compound after complete elimination of hydrogen from the material.