Using sequentially acquired 2-D images of microtome sections via a light microscope, 3-D models of the microstructure of commercial and laboratory produced medium density fibreboards (MDF) were constructed. To assess the accuracy of the 3-D models, they were analysed for their ratios of inter-fibre void using an image analysis technique. The study indicated that it was feasible to use this technique to determine the variation in inter-fibre void ratio at different depths in the MDF. The ratio of void area varied significantly in a gradient from the top/bottom of the boards to the core (middle). However, in the other directions (along the length and breadth), there were no significant differences in the void ratio. The ratio of void area within each panel was negatively related to the density