5-Hydroxy- and 6-hydroxy-4- methylcoumarins and their methyl ethers and methyl 5-hydroxy-4-methylcoumarin-6-carboxylate have been chloromethylated using different molecular proportions of paraformaldehyde. Structures of the ch loromethylated coumarins have been established by comparison of the methyl derivatives, obtained on reduction, with compounds of known structures.