The catalytic deep oxidation of benzene, toluene and xylene over NaY, CuY, PdHY and PdY zeolites has been investigated in the temperature range 493-623 K. PdY is the most active catalyst even at low Pd content while CuY achieves distinct catalytic activity only at higher Cu content. Reductive pretreatment increases the conversion for PdY but decreases the activity of CuY. The formation of Pd(0) clusters which are supposed to be transformed into PdnOm phases is suggested to be the active species for the combustion process. As cluster formation and coke decomposition are suppressed in PdHY, the lower activity of the protonated sample may also be explained in this way. Under the same reaction conditions, toluene and xylene are more reactive than benzene. There is a remarkable enhancement of the PdY activity when toluene is added to the benzene feed. Water admission lowers the conversion only at low temperatures while at higher temperatures, there is no adverse effect. In all cases, only CO2 and water were observed as the products and neither CO nor organic by-products were detected.