We investigate the evolution of particle size distribution of incipient soot formed in laminar premixed n-dodecane-oxygen-argon flames. The flames are established on a porous flat flame burner with equivalence ratio equal to 2 and a maximum name temperature of 1800 and 1870 X. Detailed size distributions are obtained by the burner-stabilized stagnation (BSS) flame sampling approach using a,scanning mobility particle sizer. The flame temperature profiles fire determined for each separation distance between the burner surface and stapation surface/probe oririce, It is shown that the flames can be modeled closely using in opposed jet flame code without having to estimate the effect of probe perturbation, The measured and simulated temperature profiles, show good agreement. The evolution of lie soot size distributions for n-dodecane flames are similar to those observed in ethylene flames, The size distributions are characteristically bimodal, indicating strong, persistent nucleation over a large range of residence times in the flame. Under similar conditions, the nucleation mode in the n dodecane flames is stronger than that in comparable ethylene flames.