Ar:O-2 low pressure plasma (Ar:O-2 LPP) surface treatment is proposed for increasing the surface energy and improve the adhesion of wood-polyethylene composite. The treatment time was varied between 20 and 90 s and the configuration of the shelves inside the plasma chamber (direct and secondary downstream) was also changed. Ar:O-2 LPP treatment during 30-40 s created new surface carbon-oxygen groups, increased the surface energy, mainly its polar component, reduced roughness and caused ablation of wood-polyethylene composite, irrespective of the configuration of the shelves inside the plasma chamber. The increase of the treatment time above 40 s did not cause additional surface modifications. Adhesion of the wood-polyethylene composite was noticeably increased when was treated with Ar:O-2 LPP. The surface modifications of Ar:O-2 LPP treated wood-polyethylene composite were partially lost during 24 h after treatment.