In this work, the correct placement of a Rushton disk turbine in reactors for improving gas-liquid mass transfer has been studied experimentally in the case of surface aeration, and in particular, the power input through surface aeration is compared with that through sparger aeration. It is found that in the case of surface aeration the power input at a fixed value of the mass-transfer parameter k(L)a decreases as the turbine moves towards the static liquid surface. Moreover, it is interesting to find out that, for the standard sparger aeration to get the same k(L)a value at low or intermediate gassing rates, the power input can be greater than that for the surface aeration with the turbine placed very near the static liquid surface.