Selective ethylation of phenol with ethanol to para-ethylphenol, over pore size tailored ZSM-5 zeolite, has been studied. Fine control of pore openings of ZSM-5 was achieved by chemical vapour deposition of silica employing tetra-ethyl orthosilicate, Selectivity for para-ethylphenol increased with the extent of silica deposition and under a comparable phenol conversion level, pore size controlled ZSM-5 exhibited about 88% selectivity for para-ethylphenol, as compared to only 37% with unmodified ZSM-5. The influences of various reaction parameters, e.g., temperature, WHSV and phenol to ethanol mole ratio were also studied. Addition of water to reactants improved the selectivity for ethylation, as well as selectivity for para-ethylphenol, and also stability of the catalyst. A comprehensive scheme for selective phenol ethylation to para-ethylphenol has been proposed.