PAH/soot has been modeled in two types of laminar counterflow diffusion flames using a detailed reaction mechanism based on the sectional method. The two flames differ mainly by their fuel type: ethylene versus benzene. Their sensitivity to the strain rate is analyzed with respect to the total PAH/soot mass density and number density, as well as the particle size distribution function. A strong sensitivity to these parameters has been confirmed, in line with experimental data. The chemical production rates of the first two moments of the PAH/soot particle size distribution functions are found to be a moderate function of the strain rate. These observations are explained by a scaling analysis. The current application of the detailed mechanism in different diffusion type of flames gives valuable information on its width of applicability, and can be used for the optimization of the model parameters.