In spite of different studies describing the effect of interspecific variability on wood thermal degradation, no study describes the effect of intraspecific variability of wood. As physical properties as well as chemical composition of wood can vary between stands and even within tree, the effect of radial position of European oak wood (Quercus petraea Liebl.) on its thermal stability was investigated. Samples of heartwood, sapwood, juvenile wood, earlywood or latewood taken from the radii of two trees were ground to fine sawdust before subjecting to thermogravimetric analysis (TGA) at 220 °C for 2 h. At the same time, holocellulose, cellulose and extractives as well as extracted heartwood and sapwood were also subjected to TGA using the same procedure. Results indicated that heartwood was more sensitive to heat than sapwood, the inner side of heartwood being more sensitive than the outer side. Differences were also noticed between native and extracted wood, the latter being less sensitive to thermal degradation. These results were consistent with the stability of each wood cell wall component indicating that extractives were more susceptible to thermal degradation than holocellulose, holocellulose being more susceptible than cellulose. At the ring level, earlywood was shown to be more sensitive to thermal degradation than latewood.