AbstractThis work reports adhesion behaviour of polyethylene on paper, and deals with the surface energy of the materials involved in the manufacture of these composites, and its influence on the adhesion strength, at constant roughness, for the paper substrates. The surface energy of different papers treated with various sizing agents was determined by measuring contact angles according to the Owens‐Wendt method. The peeling energy was shown to follow a linear relationship versus the reversible energy of adhesion. This result is explained by the fact that rupture takes place at the interface and that the size of the defect at the interface depends on the spreading coefficient. Corona treatment, applied to strongly sized papers before making the composites, restored the adhesion strength to its original range of values, again demonstrating the thermodynamic character of adhesion in thermoplastic‐paper composi