Numerical simulation and experimental studies have been conducted on the effect of particle size distribution on the surface roughness and porosity for thin particle layers. When particles with wide size distribution are deposited on the test surface, surface roughness of the particle layer increases. The degree of surface roughness also increases when the particles are agglomerated. Numrical simulation indicates that the porosity becomes lower when non-agglomerated particles with narrow particle size distribution are used. On the other hand, the porosity becomes lower when agglomerated particles with wide particle size distribution are used. From the experimental results, porosity of the particle layer decreases when particles with wide size distribution are used. This is because of the particle agglomeration. It is also found from numerical simulation that the number of closed void spaces in the particle layer increases when agglomerated particles with wide size distribution are used.