Wood composites prepared with a series of precisely cut wood elements were used to investigate the influence of raw material characteristics on horizontal density distribution (HDD). The effect of flake size on HDD was dependent on specimen size. Two aspects of voids, the frequency and the size, were identified as being responsible for this dependence. In addition, a layer concept was developedto relate flake thickness, board thickness, wood density, and board density to HDD. Board uniformity improves as the number of flake layers increases