The molecular mechanism, the kinetics and the process development of photocrosslinking of diene elastomers, of high density and low density polyethylenes, and of new linear and dendritic unsaturated polyesters using UV-irradiation are described. New methods for modification of various polymers by surface photografting are presented, the effects on adhesion and adsorption, and the mechanism of the reactions related to the shortlived high energy states of aromatic ketones as initiators are presented and discussed. The development of surface photografting as a new method for UV-initiated lamination of various polymer films and sheets is described, the molecular mechanism and the kinetics of the reactions are discussed, and the mechanical and barrier properties of the laminates are presented.