Luminescent silicon nanoclusters have been formed in silicon-rich silicon nitride and silicon-rich silicon oxynitride films grown using inductively coupled plasma chemical vapour deposition. The luminescent properties and electronic structure of the films have been investigated through ultraviolet-excited photoluminescence and synchrotron-based X-ray absorption spectroscopy experiments at the Si K-and L3, 2-edges, respectively. In the silicon-rich silicon nitride films, luminescence in the visible was observed from quantum confinement effects and inter-bandgap defect levels while X-ray absorption spectroscopy indicates a structural reordering of the silicon nanoclusters and nitride host matrix with increased silicon nanocluster phase separation, occurring at lower annealing temperatures in more silicon-rich films. Luminescence from the silicon-rich silicon oxynitride films appeared to be defect-related and only the silicon oxide and nitride host matrices exhibited structural reordering when annealed, while there was no change in the structure of the silicon nanoclusters.