A comparative study on the disproportionation of toluene on cobalt-modified (2.5 wt %) zeolites ZSM-5 and synthetic and natural mordenites was performed, and the main features of the effect of CO2, on this process were revealed for the most active catalyst (synthetic mordenite). It was established that the action of CO2 on toluene disproportionation was accompanied by an increase in the conversion and a decrease in the temperature of achieving the limiting activity (45.5%) of the synthetic mordenite catalyst. The influence of preliminary treatment on the acid strength distribution in synthetic mordenite was studied, and CO2 was found to have no effect on the acidity spectrum. The mechanism of the promotion effect of CO2 was proposed.