Pyrolytic behavior of benzyl-substituted naphthalenes, phenanthrenes, anthracenes, and fluorenes as coal model compounds has been investigated. The reaction was carried out at 430 degrees C in a sealed tube in the presence or absence of 9,10-dihydroanthracene (DHA) as a hydrogen source. The results obtained are as follows. (a) alpha-Substituted type substrates 1,5-dibenzylnaphthalene, 9-benzylphenanthrene, and 9-benzylanthracene selectively give toluene as the cleavage product along with the corresponding polyaromatic fragments accompanied by formation of oligomeric products. The cleavage reaction possibly proceeds by initial ipso-hydrogen addition, which appears to be enhanced by addition of DHA. (b) The major reaction of beta-substituted type compounds 2,6-dibenzylnaphthalene, 2- and 3-benzylphenanthrenes, and 2-benzylanthracene is oligomerization which may involve radical intermediates formed by hydrogen abstraction from the substrates and from the oligomers benzene may be selectively liberated as the volatile product, with the exception of the reaction of 2-benzylanthracene, In the presence of DKA, toluene can also be formed together with benzene, as for the alpha-type compounds. (c) The thermal behavior of 1-, 2-, and 4-benzylfluorenes is rather similar to that of the beta-type compounds.