The MCM-41 and zeolite Y exchanged with Li⁺, Na⁺, K⁺ and Cs⁺ were used as catalyst for Diels–Alder reaction of cyclopentadiene (CPD) with p-benzoquinone (PBQ) and some derivatives to achieve higher reaction rate and diastereoselectivity. The 2:1 CPD–PBQ adducts of endo-anti-endo and endo-anti-exo obtained, respectively, in the case of PBQ as the major product in the presencece of MCM-41 and CsY is remarkable. Semiempirical calculation by PM5 method was carried out to define the energetics of the system and Goering–Schewene diagram under the catalytic effect of BF₃ and AlCl₃ Lewis acids. It was found that even though the endo-anti-exo is thermodynamically more stable than endo-anti-endo in uncaytalyzed Diels–Alder reaction, the latter is the more stable isomer in the presence of Lewis acid catalyst.