The oxidative dehydrogenation of propane was investigated in a fixed-bed tubular flow reactor at 350 and 450 degreesC over V-Mg-O catalysts prepared via a solid reaction ( the mix-VMg catalysts) or from mesoporous precursors ( the meso-VMg catalysts). Significantly higher selectivities and yields to propene were obtained over the meso-VMg catalysts than over the mix-VMg ones. The cooperation between a much higher BET specific surface area and a novel phase, a highly dispersed-Mg-in-V2O3, is suggested as responsible for the higher ODP performance of the meso-VMg catalysts than of the mix-VMg ones.