Acidic zeolites, especially faujasites, efficiently promote the intramolecular cyclization of aryl propynoates and propynethioates, which produces coumarins and thiocoumarins, usually in high yields. Comparison with homogeneous Lewis or BrØnsted acids and with heterogeneous related sieve materials revealed the prevalence of zeolites exhibiting large cage-type pores (H-USY) for such cyclizations. Various substituents proved compatible with the cyclization process, leading to a variety of substituted coumarins and thiocoumarins (20 examples, 30–99 %).