Oxidation by molecular oxygen of freshly produced soot from a flat ethylene-air-flame is investigated under well-controlled conditions in a flow reactor at 773-1273K and atmospheric pressure. Soot particles are characterized before and after oxidation by electrical mobility technique. In addition to the size-classified soot number density, the molecular gas-phase species are obtained simultaneously by molecular-beam mass spectrometry. Oxidation behavior of soot particles as well as some hydrocarbon species sampled from the soot source was determined quantitatively. Oxygenated species are formed as molecular intermediates during the oxidation process inside the reactor. Different particle size distributions have been investigated by varying the sampling position and equivalence ratio of the flame. Oxidation of soot starts at different temperatures, but is clearly separated from oxidation of flame species starting earlier at lower temperatures. Soot oxidation rates were calculated and comparison with the Nagle-Strickland-Constable model indicates that the investigated flame-sampled soot is more reactive than graphite under the investigated conditions. The presented dataset may help to validate existing soot models.