The course of Bell-Boudoir reaction (2CO &rarr CO2 + C) on the catalysts of hydrocarbon synthesis from CO and H2 was studied. It is shown that, with cobalt-based systems, this reaction is practically absent, whereas, under conditions of arene synthesis from CO and H2 at higher temperatures, a more intensive Bell-Boudoir reaction was observed. The basic regularities of CO conversion to CO2 in the presence of bifunctional Co-high-silica zeolite catalysts were established.