High-temperature contact of pyridine with the surface of dealuminated mazzite leads to the appearance of infrared bands at 2914, 2848, 1496, and 1462 cm-1, and to an ultraviolet signal at 205 nm, distinct from those attributable to pyridinium ions and coordinated pyridine. It is proposed that the species responsible for these features correspond to conjugated iminium ions (dihydro-pyridinium ions) formed by a nucleophilic attack and protonation of pyridine molecules adsorbed on Lewis sites. Their formation would then involve the participation of strong Lewis/Bronsted pairs of sites that could correspond to the superacid site often invoked in zeolitic materials.