The alkylation of ethylbenzene in the presence of other aromatic compounds has been studied over a pore size regulated MFI zeolite. The aromatic compounds chosen were of various kinetic diameter, hence they were expected to hinder the movement of reactant molecules both on the external surface and within zeolite channels. It was observed that some of the aromatic compounds got alkylated along with ethylbenzene. The effects of varying the concentration of aromatic compounds in the feed on ethylbenzene conversion and product distribution have been discussed.