The main objective of this thesis is to obtain a better understanding of adhesive contacts and their frictional behaviour. Both natural and man-made surfaces are rough over a wide range of length scales. Tribological studies of rough surfaces need to account for the interactions between these asperities. In this work a sim- ple atomistically–inspired macro-scale model is developed to study smooth and rough contacts between elastically deformable bodies where adhesion and fric- tion are simultaneously active at the interface. A full description of the model is presented in Chapter 2. There, the Green’s function molecular dynamics (GFMD) technique is extended to explicitly de- scribe the two solids in contact and their mixed-mode interface interactions. The interactions between surfaces are described through a coupled cohesive-zone model implemented in the GFMD technique. The extended GFMD technique includes an incremental iterative scheme, which is necessary to capture the con- tact area evolution when tangential tractions develop at the interface between the solids under loading.