Silynation of ZSM-5 zeolite by CVD technique and its advantages are reported. Modification by this technique passivates the external surface and thereby reduces the non-selective surface reactions. Further, the Bronsted acid sites are increased with successive silynations at the cost of Lewis sites. With increasing silynation narrowing of pore mouth was observed which enhanced the paraselectivity in the ethylbenzene disproportionation reaction. The observations are based on the results of FT-IR, MAS-NMR, TPD of ammonia and catalytic test reactions.