The study investigated the extent to which the properties of MDF boards change with changes in the moisture of fibers forming mats from 4.5 to 10.5%. MDF panels were produced in the laboratory with an assumed density of 660kg/m3 and a thickness of 12 mm. It has been found that it is possible to produce boards without their delamination in the whole range of humidity of fibers. The increased amount of water vapor in the mats when they are pressed is likely to influence better plasticization of the fibers, which translates to improved properties of the boards. Increasing moisture content from 6.5 to 10.5% increases the modulus of rupture by approx. 9%, the modulus of elasticity by approx. 7%, intemal bonds by approx.30% and reduces swelling by approx. 22%.