The polyethyleneamines ethylenediamine (EDA) and diethylenetriamine (DETA) can be considered as promising CO2-capturing solvents, producible from renewable resources. In the present work, kinetics of CO2 reactions with EDA and DETA was investigated by using a stirred-cell reactor. The molarities of EDA and DETA in the aqueous solutions were varied from 0.1 to 0.4 and 0.1 to 0.5, correspondingly. The observed pseudo-first-order reaction rate constants were measured at 303, 308, and 313K. The zwitterion and termolecular mechanisms were used to correlate the rate constants. DETA was found to have higher reactivity with CO2 than EDA. Second-order rate constants for the reactions with EDA and DETA were equal to 15770 and 21480m(3)/(kmols) at 303K. The activation energy values for EDA and DETA were found to be 57.7 and 30.2kJ/mol, respectively.