Zinc oxide nanopowders were synthesized by a solution combustion technique named impregnated layer combustion synthesis (ILCS), involving the impregnation of an active layer with the reactant solution and subsequently the combustion of the impregnated system. In this work three different organic fuels and two different ignition modes were tested in order to optimize the final microstructure and specific surface area (SSA) of the ZnO nanopowders. In particular, the ignition mode was found to significantly affect the final products, discriminating between an explosion procedure (flame combustion) and a self-propagating mode (smoldering combustion). The nitrate-glycine mixture and the smoldering combustion way were found to be the most suitable conditions, giving rise to softly agglomerated nanopowders with an average size of 20 nm and a very high SSA, without the need of any further crystallization treatment.