Pyrolysis of KOH impregnated wood is investigated by means of thermogravimetric analysis and a packed-bed reactor. Apart from a confirmation in the trend of product yields and composition versus the additive content, profound modifications in the devolatilization curves and the bed thermal field are for the first time observed. For KOH contents up to about 1 wt %, the effects are essentially of catalytic type. The usual shape of the therrnogravimetric curves is preserved though with a progressive displacement at significantly lower temperatures. For higher KOH contents, also associated with wood structure deterioration during aqueous impregnation, even the qualitative features are altered. The bed heating dynamics are strongly modified by the enhanced reaction exothermicity which, for high KOH contents, tend to turn the role of the external heat source simply into a starter for a self-sustaining process. The magnitude of the exothermic effect display, also including pyrolytic runaway, depends on the additive percentage and the heating conditions.