[en] Zeolites catalyze chlorination of aromatics by sulfuryl chloride SO2Cl2. It is possible by an appropriate choice of the catalyst to effect at will, with very high selectivity, either the ring or the side-chain chlorination. Zeolite ZF520 is the choice catalyst for the former, because of its high Brønsted acidity. Zeolite NaX (13X) is a fine catalyst for the latter, free-radical chlorination; the reaction is best effected in the presence of a light source; the catalyst can be re-used many times with no loss in activity. Both reaction modes, the ionic (ring chlorination) and the radical (side-chain substitution), are likely to occur outside of the channel network in the microporous solid. The effects of various experimental factors -such as the nature of the solvent, the reaction time and temperature, the Brønsted acidity of the solid support, the presence of radical inhibitors, the quantity of catalysts- were investigated. The procedures resulting from this study are very easy to implement in practice and are quite effective.