Computer simulations of kinetic phenomena have been carried out for a general soda-additive delignification mechanism consisting of an equilibrium process, followed by an irreversible step in which the additive participates. Simulations have been performed under conditions where the concentration of additive is either at steady state, or declines with time. The results clearly show that caution should be exercised in interpretation of experimental data when attempting to use kinetic results to elucidate details of reaction mechanisms. In particular, it is shown that the origin of exprimentally observed dependencies on additive concentrations such as a “square-root” relationship can be explained by assuming different ratios of rate constants for formation and subsequent decomposition of a quinone methide intermediate.