X-ray absorption spectroscopy (XAFS) has been used to characterise the local environment around Cu + ions in two types of glasses of base composition LaMgB 5O 10 and LiLaP 4O 12. In both glasses, Cu + is surrounded by two oxygens respectively at 1.87 and 1.86 Å. For the first time in glasses, the formation of Cu +Cu + pairs ( d CuCu = 2.35 Å) is clearly evidenced in the phosphate. These results will be discussed with respect to the crystal chemistry of Cu(I) in copper oxides and the specific luminescent properties of an isolated Cu + centre or Cu +Cu + pairs.