Printing papers contain both chemical pulp and mechanical pulp. Chemical pulp fibres are commonly used as reinforcement, while mechanical pulp maintains opacity and printability. Modelling was performed to provide hypothetical interrelationships between strength and bonding capacity of the fibres. It is suggested that the paper strength, within certain limits, is described by the number and type of bonds occurring in the fibre network. The number of possible bonds was determined as the optically active total area of the fibres, i.e. the light scattering coefficient. Actual bonds occur only when potential bonds are accessible, and accessibility should be improved with increased fibre flexibility and compressibility. It implies that paper sheet density has to be introduced into the model along with the light scattering coefficient. In addition, the tensile strength of the paper is supposed to depend on rheological conditions, i.e. shearing speed that is determined as the tensile speed, and viscoelasticity of the paper describing the type of bonds.