The structure of YFe 2 D x deuterides (x ؍ 1.3, 1.9, 1.75, and 2.6) have been studied by neutron diffraction (ND). The influence of a thermal treatment on the synthesis of YFe 2 D x deuterides has been followed by in situ neutron diffraction for x ؍ 1.3 and 1.9. After deuterium absorption at room temperature, their diffraction patterns show a mixture of YFe 2 and a deuteride phase YFe 2 D y (2.3 < y < 2.6). Heating the samples above 400 K for x ؍ 1.3 and 425 K for x ؍ 1.9, leads to a deuterium diffusion from the deuterium rich phase toward YFe 2 to form a single phase deuteride with lower D content. Single phase deuterides YFe 2 D 1.3 , YFe 2 D 1.75 , and YFe 2 D 1.9 display superstructure lines which imply a lowering of symmetry compared to the cubic C15 structure of the parent intermetallic. YFe 2 D 1.3 crystallizes in the tetragonal I4 space group (Z ؍ 20) with a ؍ 11.985(2) A > and c ؍ 7.622(1) A > , YFe 2 D 1.75 in the cubic I4 3m space group (Z ؍ 64) with a ؍ 15.336(2) A > , and YFe 2 D 1.9 in a tetragonal structure with a ؍ 12.145(2) A > and c ؍ 23.064(2) A > . The analysis of their ND patterns at 300 K shows for x ؍ 1.3 and 1.75 an ordering of the deuterium atoms in some preferential tetrahedral Y2Fe2 sites and a ferromagnetic structure with 1.5 and 1.9 B/Fe, respectively. For YFe 2 D 1.3 and YFe 2 D 1.9 the superstructure lines disappear above 460 and 444 K, respectively, and they return to a C15 structure. The origin of the structural deviation and of the order-disorder transition is discussed in relation with deuterium and magnetic ordering. YFe 2 D 2.6 deuteride crystallizes at 300 K in the cubic Fd3m space group (Z ؍ 8) with a ؍ 7.785(2), deuterium atoms located statistically in tetrahedral Y2Fe2 sites and a ferromagnetic structure with a magnetic moment of 1.8 B/Fe.