Phenol-formaldehyde (PF) resins are extensively used as adhesives and binders for lignocellulosic materials. Lignocellulosic materials, conversely, are often used as fillers for phenol-formaldehyde resins in many of their applications. Adhesion between an adhesive and an adherend can be described as a physicochemical phenomenon, and the interaction between PF resins and cellulose is no exception. In the case of the interaction of PF resins with cellulose, the causes of adhesion are thought to reside mostly with the attraction between resin and adherend due to secondary forces, such as van der Waals, H-bonding, and electrostatic, between noncovalently bonded pairs of atoms and atom groups. Although it is well known that formaldehyde and formaldehyde-based resins to a limited extent also react covalently with cellulose to form ether linkages and to crosslink cellulose fibers [1], the contribution of such covalent bonds to the phenomenon of PF adhesion in the bonding of lignocellulosic materials does not appear, to our knowledge, to have been assessed qualitatively or quantitatively. It has been disregarded, consequently, also in our calculations.