The acylation of benzofuran and of 2-methylbenzofuran by acetic anhydride was carried out over a Y zeolite (Si/Al atomic ratio = 16) in a dynamic flow reactor at 60 degrees C, under atmospheric pressure. Deactivation was significant for benzofuran, but much less so for 2-methylbenzofuran with which high yields (about 100% conversion with 95% selectivity in 3-acetyl-2-methylbenzofuran) could be obtained. 2-Methylbenzofuran was about twice as reactive as benzofuran, the position 3 in 2-methylbenzofuran being at least two orders of magnitude more reactive than the position 3 in benzofuran. The difference in the aging process is attributed to a difference in the nature and the location of the irreversibly adsorbed material.