The complete crystal structure of Ca2RuD6 has been determined by neutron powder diffraction: space group Fm3m, K2PtCl6 structure, as found for other hexahydrides salts of the group 8 metals and with alkaline earth or lanthanide counter ions.  No structural phase transition was observed between 340K and 50K.  The deuterium nuclear quadrupole coupling constant, 54.7 kHz, led to an ionic character of the Ru-D bond of 76%.  Some known trends in the behavior of A2MH6 salts are being  interpreted in terms of the ionization energies of the cation and central metal atom.