Recently, the reaction system of isopropylation of naphthalene over USY and H-mordenite zeolites was comprehensively treated experimentally as well as computationally by Buijs et al. [1]. Results from both sources were used to discard shape selectivity as an explanation for the observed product distribution. In this contribution, it is shown that their computational argument cannot be used for this purpose, since after the improvement of their orthogonal projection method, it gives very similar results to those criticised in their paper. (C) 2011 Elsevier Inc. All rights reserved.