Components of polymerized pitches are of large molecular size and consequently difficult to characterize. Moreover, pitches with similar degrees of polymerization obtained by different treatments have similar properties brit different molecular structures. Selective oxidation with RuO4 has proven to be a suitable method for the elucidation of structural details in other complex carbonaceous substances such as coals, asphaltenes, or kerogens. In this paper the behavior of some model compounds was studied in order to achieve a better understanding of how this specific oxidation affects several possible pitch structures. To improve the efficiency of the reaction, an ultrasonic bath was used. Highly condensed compounds such as coronene and triphenylene were the most reactive, as they were the most oxidized of all the compounds tested. On the other hand, it was found that aryl-aryl bonds are very stable. The ability of RuO4 to distinguish between different molecular structures could be used as a new tool in the chemical characterization of polymerized pitches.