Luminescence features of cross-linked polyethylene samples peeled from high voltage cables have been investigated. Special emphasis is given to the effect of crosslinking by-products on the emission. Photoluminescence and luminescence following excitation by a silent discharge have been examined in order to identify which of the luminescent centres are optically active following electrical charge recombination, and could therefore act as charge traps. Both fluorescence and phosphorescence contain signatures of volatile and bound species. However, the identification of the origin of these emissions is far from complete. The signature of acetophenone has been clearly identified in the phosphorescence spectra. Radiative charge recombination involves the long lived components of the phosphorescence spectrum, i.e. the lowest lying triplet states. Some routes are given for identifying more precisely the origin of the emissions.