A theoretical analysis of the influence of particle size distribution on observed TOF dependence on cluster size is presented for a two step catalytic cycle. Such mechanism can display different TOF behavior including maxima. In the later case simulations demonstrated broadening of TOF curves compared to an idealized case of very narrow PSD. However, for more often observed cases with smooth TOF increase or decrease with cluster size increase incorporation of particle size distribution in kinetic analysis is not required at least for often experimentally observed particle size distributions.