Various factors affect the equilibrium moisture content in particle boards; so as thickness of the board, type of the board, and type of the resin. 4 different types of particle boards were used for our experiment. They were cut into 24 samples; their size was 50 mm X 50 mm. First, samples were moistened in a climate with 34 %, 65 %, 75 %, 90 % and 98 % atmospheric humidity, maintaining the constant weight of the particles. After moistening, the boards were dried using the same climates as before, and then put into a dryer with 103+-2 °C. Changes of weight and swelling were observed. P5 samples glued by melamine-formaldehyde resine turned out to be the best. OSB3 samples glued by isosyanate resin turned out well up to 90 % humidity; then the swelling increased significantly. Among P2 samples glued by urea-formaldehyde resin the thinner samples turned out to be better from the thicker ones.