The very different optical spectra found for the green coloured Y2BaNiO5and the substituted brown-tobacco Y2BaNi1−xZnxO5oxides have been explained taking account the different crystal structure which show these oxides. In this sense, Y2BaNiO5shows orthorhombic symmetry, space group Immm, with the nickel situated in a distorted octahedral coordination giving rise to a site of D4has local symmetry. The substituted Y2BaNi1−xZnxO5which are isostructural crystallyze with orthorhombic symmetry, space group Pnma showing as main characteristic the existence of isolated distorted square pyramidal coordination for the nickle NiO5which yeilds aproximately C4vas point symmetry.