We report the preparation and cathodoluminescent properties of rare-earth-doped Y2O3-SiO2 thin films. The thin films were prepared by magnetron sputtering. By doping with Eu3+, Tb3+ and Ce3+, most as-deposited amorphous thin films show luminescence. High temperature annealing above 800 degrees C increases the luminescence intensity 5-10 times. This reveals that the crystal field is dominated by the nearest atomic neighbours. The primary colours needed for a full-colour display can be realized by doping with Eu3+, Tb3+ and Ce3+.