Hierarchical (or mesoporous) zeolites have attracted significant attention during the first decade of the 21st century, and so far this interest continues to increase. There have already been several reviews giving detailed accounts of the developments emphasizing different aspects of this research topic. Until now, the main reason for developing hierarchical zeolites has been to achieve heterogeneous catalysts with improved performance but this particular facet has not yet been reviewed in detail. Thus, the present paper summaries and categorizes the catalytic studies utilizing hierarchical zeolites that have been reported hitherto. Prototypical examples from some of the different categories of catalytic reactions that have been studied using hierarchical zeolite catalysts are highlighted. This clearly illustrates the different ways that improved performance can be achieved with this family of zeolite catalysts. Finally, future opportunities for hierarchical zeolite catalysts are discussed, and the virtues of various preparation methods are outlined, including a discussion of possible pitfalls in the evaluation of new, potential hierarchical zeolite catalysts. (C) 2011 Elsevier B.V. All rights reserved.