A number of 9-[(arylmethoxy)methyl]anthracenes were prepared and their photoreactivity was studied. The intramolecular [4π+4π]cycloaddition competes with the intermolecular head-to-tail [4π+4π] cyclodimerization. The aryl substituents control the selectivity; concentration only plays a role in selectivity in certain cases. The complete reversibility of the cycloaddition makes this process suitable