Danckwerts and film theories have been compared through the aqueous ozonation kinetic study of three organics: crotonic, cinnamic and 0hydroxycinnamic acids. At the conditions investigated, these compounds areremoved from water exclusively by direct reactions with ozone and the kinetic regime of ozone absorption corresponds to a fast second order irreversiblereaction. In this regime, Danckwerts theory provides wider possibilities than film theory for the determination of the rate constant and individual liquid side masstransfer coefficients. The ozonation reactor was operated as an agitated cell to determine the rate constant and as an agitated tank to obtain the mass transfercoefficient. Rate constants were found to increase with increasing pH. AtpH 7 the ozone reactivity of these compounds was in the following increasing order:Cinnamic acid <⃒ crotonic acid <⃒ o‐hydroxycinnamic acid. AtpH 3 differences in reactivity were not significant.