This work deals with the dealumination of zeolite beta under different conditions to optimize its catalytic performance. The dealumination was carried out either using oxalic or tartaric acid solution of different pH values or steaming up to 500 degrees C. The dealuminated zeolite samples were characterized using X-ray diffraction, N-2-physisorption, ICP, Al-27 NMR and NH3-TPD. Their catalytic activities were studied for acylation reaction of 2-methoxy naphthalene or naphthalene with acetic anhydride and esterification of benzyl alcohol with hexanoic acid. Among the dealuminated samples examined, those treated with oxalic acid or tartaric acid at pH 2 showed high activity. The high activity can be correlated with the relative increase in the amount of strong acid sites and with the enhanced accessibility of the reactants to the active sites, which are caused by removal of extra-framework Al species on the acid treatments.