Phosphate glasses containing transition metal oxides, such as MoO3 and WO3, are of interest for various applications making use of their electrical properties. MoO3 and WO3 are expected to have very similar chemical and structural behaviour, but surprisingly their DC conductivity shows a sharp difference, by up to six orders of magnitude at high MO3 content (M=Mo, W). Structural differences between Mo and W phosphate glasses have been proposed on the basis of Raman spectroscopy. We wish to investigate the possible structural differences by a preliminary neutron diffraction experiment. The structure of related crystals indicates that the short range order may be unusually complex, and yet very well suited to study by neutron diffraction.