Obtaining good bonding between two dissimilar materials is critical for several aspects in textile finishing, processing and application, including the durability of common textile finishes and fabric coatings, and the performance of fiber reinforced composites. Both functional properties and long term performance are dependent on the effective adhesion between the fiber on one hand and finishing agent, coating polymer or resin on the other. It is generally accepted that good adhesion is achieved through covalent chemical bonding, acid-base interactions or hydrogen bonding, surface energies that favor complete wetting of the fibers, large specific surface area of fibers, and surface roughness that allows lock and key type mechanical bonding. In practice, various surface treatments have been applied to fibers to alter their surface characteristics and to improve their adhesion properties. For example, chemical modifications such as acid oxidation, corona or plasma pre-treatments have been commonly employed. This paper aims to provide some insight into photon-based processes which, depending on the spectral range of radiation and the characteristics of the radiation sources, can be used to bring about chemical as well as morphological changes to fiber surfaces. We have considered two major applications of surface modification; ( 1) textiles for improving adhesion to finishes and (2) fiber/resin adhesion enhancement in fiber reinforced composites to improve their mechanical properties. The technical approaches cover photo-chemical surface modification and micro-roughening of fiber surfaces using monochromatic UV lamps and pulsed UV excimer lasers. (C) Koninklijke Brill NV, Leiden, 2010