The effect of plasma treatment on strength properties of wood-based composites was studied. Veneers were obtained from beech logs (Fagus orientalis L.) and treated with 3 % of Tanalith E and Celcure AC-500. Two types of gasses (O-2 and N-2) were tested for plasma treatment. The effect of plasma treatment on bonding shear strength, bending strength and modulus of elasticity of plywood panels were determined according to EN 314-1 and EN 310, respectively. Surface roughness, leaching, decay test against white (Trametes versicolor) and brown rot [Postia placenta (FPRL 280)] and ground contact test of plywood samples were evaluated after plasma treatment. Results showed that plasma treatment with O-2 increased the bonding strength of plywood compared to control and treated groups. However, plasma treatment slightly increased the mass losses caused by white rot, but decreased mass losses caused by brown rot in some groups. Regarding leaching test, plasma treatment slightly increased the leaching rate of copper in some groups. Ground contact test revealed that there was no delamination in bonding line on the plasma-treated samples.