Influence of particle sizes on roughness of particle board surface was researched. To make particle boards pinewood particles received from Lesna, Otiški vrh, were used. The particles were sifted to 2 different fractions, one part of them was ground additionally, the other thermically treated. Using the procedure of wet grinding fibers were produced. 3 different types of particle boards and one particle board with an external layer were made. Various particle sizes or fibers were used for each board type and the particle board with external layer made from fibers. To measure the surface roughness a device measuring a longer surface roughness capture was made. In this way the surface roughness and density profiles of particle boards were measured and compared. It was found out that the surface roughness depends on the density of particles and fiber boards. The higher the density of the surface layer the smaller the surface roughness of boards. Surface roughness is smaller on the bottom side of particles and fiber boards than on the upper one. The difference is caused by the pouring of particles to the bottom during the particle board forming and transferring to the press. The bottom side of particle boards has higher quantity of small size particles.