In this paper, the bond quality related to the thickness of particle- and fibre- based panels was tested. Particleboard, OSB and MDF boards were tested. Five areas across the thickness of each panel were defined, where grooves were cut out, representing the area with different densities. The goal of making the grooves was to determine the bond strength of the panel in a precisely specified area. We found out that the particleboard has the highest correlation between the bond strength and the density of a particular area, followed by the OSB board, and lastly by the MDF board with the lowest correlation. We determined that the highest bond strength was in the area close to surface, which corresponds with the area of the highest density. The lowest bond strength was found in the areas with the lowest density; however that was not always in the middle of the board. For particleboard and MDF the bond strength in the surface to core layer transition area and in the core layer were almost the same. The tested OSB board has a lower bond quality in the lower surface layer due to the strands morphological characteristics.