The short-range order in semiconducting xCu 2Se · (1 − x)As 2Se 3 and mixed conducting xCuI · (1 − x)As 2Se 3 glasses has been investigated using Extended X-ray Absorption Fine Structure (EXAFS) measurements at the Cu, As and Se K-edges. A non-tetrahedral local coordination of copper, either by Se or by Se and I, has been found in these glassy systems. The pyramidal AsSe 3 units remain essentially intact on introducing Cu 2Se or CuI. However, the average selenium coordination number, N Se–Y, where Y=As or Cu, increases with x from 2.0 to 2.5–2.6. Simple stoichiometric relationships account for the observed changes in N Se–Y for the Cu 2Se–As 2Se 3 glasses, which suggest that, at a nearest neighbour level, the average selenium environment consists of two relatively weakly interacting components coming from vitreous As 2Se 3 and a hypothetical glassy Cu 2Se. On the contrary, the EXAFS results indicate that CuI is dispersed in the glass network on a molecular level and interacts with the host matrix. Favourable conductivity pathways, associated with CuI, are suggested to appear in the glass structure, which explain the improved Cu + ion conduction and copper diffusion.