Niobium-supported palladium-based catalysts (Pd, Pd-Cu and Pd-Au) were employed in the oxidation of ethanal. The catalysts were prepared according to original methods by either multi-steps (anchoring of complexes, calcination and reduction) or one-step (photoassisted reduction) procedures. The oxidation of ethanal was carried out in gas phase in a dynamic-differential reactor at 300degreesC at atmospheric pressure. The activity/selectivity of the catalysts depend on (i) the catalyst preparation; (ii) the presence of a second metal. Addition of Au or Cu decreases the catalysts deactivation and the best performance in total oxidation was obtained with Pd-Au/Nb2O5 prepared by photoassisted reduction. As shown by in situ IR spectroscopy of adsorbed CO, this peculiarity may be ascribed to Au --> Pd electron donation, which prevents the surface oxidation of palladium particles.