The oxidation of 1H-indene and 1,2-dihydronaphthalene with hydrogen peroxide in the presence of Mn(III) or Fe(III) substituted Keggin-type polyoxotungstates is described. The products obtained depend on the catalyst and reaction conditions. Ring cleavage was observed, affording dialdehydes under mild and environmentally friendly conditions. Other main products were the alpha-hydroxy-ketones. The resulting epoxides seem to be intermediates to other oxygenated products.