Isomers of C3H4 play an important role in various chemical environments. In combustion processes, the reactions of hydroxyl radicals with C3H4 isomers are critical in the overall fuel oxidation system. In the present work, mechanism and rate constants of •OH radicals with allene (H2C?C?CH2 + •OH ? H2C?C?CH• + H2O) and propyne (CH3C?CH + •OH ? •CH2C?CH + H2O) were calculated using the DFT/B3LYP and TST approaches. Results show that propyne reacts faster with •OH radical than allene at low and moderate temperatures (T ? 1000 K), opposite to the results at higher temperature regions.