In this article, the effect of one well-known inhibitor namely palmitic acid is investigated on particle size distribution of asphaltenes by imaging techniques. Pure asphaltene is extracted from crude oil to prepare Heptol (n-heptane+toluene) solutions of suspended asphaltenes. Different concentrations of inhibitors are then added to the solution. Afterward, image analysis of microscopic photos is used to determine the particle size distribution of asphaltene flocs in the presence of inhibitors. Average particle size of asphaltene and fractal structure of aggregates are also investigated; results show that the compaction of asphaltenes flocs is correlated with concentration of inhibitor. However, no significant relationship was observed between surface roughness of flocs and inhibitor concentration.