Polymers are widely used in the manufacture, converting, and end-use of paper products where the quality of polymer adhesion is important at both paper and fiber levels. This article reviews a number of relevant theories of polymer adhesion, and such adhesion phenomena as revealed in recent investigations of the adhesion between polymer thin films and paper surfaces, the adhesion of polymer molecules to cellulose fibers, and surface forces measurements between model cellulosic surfaces. It is concluded that molecular adhesion and viscoelasticity of cellulose-polymer-cellulose joints play primary roles in the paper strength, which can be tailored by a rational design of polymer additives either as strength enhancers for strong paper products or debonding agents for soft paper tissues. (C) Koninklijke Brill NV, Leiden, 2011