Data on the structure and reactivity of the catalytic systems used in the synthesis of arenecarboxylic acids by carbonylation of aryl halides are summarized. Comparative analysis of the catalytic systems on the basis of palladium and cobalt complexes in terms of the mechanism of their action, range of substrates, and synthetic uses is performed. Different aspects of the cobalt-catalyzed carbonylation of aryl halides (activity of the catalytic system, reaction chemo-and regioselectivity) from the viewpoint of the radical anion mechanism of activation of aryl halides are considered.