Simulations, based on the backward implicit method, for the square wave voltammetry (SWV) experiment are reported for the general case of quasi-reversible Butler−Volmer kinetics and a finite diffusion layer thickness. In the limiting cases of fast electrode kinetics, or semi-infinite diffusion, the results are in excellent agreement with independent calculations confirming the validity of the approach and its implementation. Under the previously unexplored conditions of finite diffusion, the effect of the diffusion layer thickness on the peak characteristicswidth, height, and voltageare identified and quantified, so providing a quantitative basis for the use of SWV at hydrodynamic electrodes for the determination of electrochemical kinetic parameters.