The effect of operational parameters on the creation of chip particles in the CNC finishing processingof wood-based materials. The object of this study was a comparison of created chips from the process of milling two wood-based materials: medium-density fiberboard, and particleboard, using a modern CNC 5-axis milling center. The materials in the form of blocks were milled at constant revolutions of the cutting tool (18,000 rev/min), with changeable variables of feed rates (8, 10, and 12 m/min), and width of cut (1, 2, and 3 mm). The size of created chips was measured by gravimetric weighing from sieving analysis of the retained volume of chips on sieves with pre-defined mesh sizes. The main emphasis was aimed at studying particles of chipsobtained in the finishing process of the milling below <0.125mm. However, the others are mentioned and discussed. Gravimetric differences of the retained volume of chip mass show that created MDF chips are mostly in the size range of <0.250 to 0.125 mm, and particleboard in the size range of <0.500 to 0.250 mm. Distribution of average values in dependence on different conditions shows a decreasing effect with increasing feed rate on the amount of very small chip particles in the volume of both materials. Increasing the feed rate can decrease the amount of very particles in the range below <0.125 mm in the volume of chip mass.