An analytical solution is presented for the concentration profiles inside a catalyst particle with uniform activity for a parallel-consecutive reaction scheme containing a reversible step and in which the reactions are all of the first order. An accurate approximate solution for the surface fluxes was developed for the case of non-uniform activity. The effects of the degree of reversibility of the first step of the consecutive chain and of the ratio of the surface concentrations of the intermediate and feed component are illustrated. The influence of a non uniform catalyst activity is shown to be important, particularly in the mixed control regime.