Catalytic activity of MCM-68 zeolite with MSE topology was enhanced by the dealumination in the isopropylation of naphthalene (NP), and maximized at SiO2/Al2O3 = 70. However, further dealumination accompanies the decrease in catalytic activity. The selectivities for beta,beta-diisopropylnaphthalene (beta,beta-DIPN) were in the level of 50%, and those for 2,6-DIPN were 40% at the SiO2/Al2O3 ratio of 70-263. The MCM-68 channels have some shape-selective natures in the isopropylation for the formation of beta,beta-DIPN; however, they are too large for selective formation of 2,6-DIPN. The increase in bulkiness of alkylating agent from propene to 1-butene and 2-methylpropene enhanced the selectivities for beta,beta- and 2,6-dialkylnaphthalene (DAN). The selectivities for beta,beta-di-sec-butylnaphthalene (beta,beta-DSBN) in the sec-butylation and beta,beta-di-tert-butylnaphthaiene (beta,beta-DTBN) in the tert-butylation were higher than 90%. Similarly, the selectivities for 2,6-DSBN and 2,6-DTBN increased: 65-75% for 2,6-DSBN in the sec-butylation and 85-98% for the tert-butylation. These results suggest that the differences are due to the steric differentiation of beta,beta-DAN from their isomers and of 2,6-DAN from beta,beta-DAN in the MCM-68 channels, and that the fitting the transition state in the zeolite channels is a key for highly shape-selective catalysis. (C) 2008 Elsevier B.V. All rights reserved.