The polyethyleneamines ethylenediamine (EDA) and diethylenetriamine (DETA) can be considered as promising CO 2 -capturing solvents, producible from renewable resources. In the present work, kinetics of CO 2 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 313 K. The zwitterion and termolecular mechanisms were used to correlate the rate constants. DETA was found to have higher reactivity with CO 2 than EDA. Second-order rate constants for the reactions with EDA and DETA were equal to 15770 and 21480 m 3 /(kmol s) at 303 K. The activation energy values for EDA and DETA were found to be 57.7 and 30.2 kJ/mol, respectively.