Selective disproportionation of ethylbenzene (EB) mixed with xylene to pdiethylbenzene (p-DEB) was studied over modified HZSM-5 zeolite. The relationship between extent of silica deposition and para selectivity was established. The effect of reaction parameters such as temperature and liquid hourly space velocity (LHSV) on para selectivity was investigated. A study of the kinetics of the reaction in the temperature range 553-598 K was carried out. The estimated activation energy value is lower than that reported for parallel disproportionation reaction with pure EB, in the literature. This has been explained on the basis of enhanced intracrystalline diffusion in the modified zeolite.