Scientific aspects of technologies based on application of non-equilibrium oxygen plasma are presented. Oxygen plasma is sustained by an electrodeless discharge to facilitate a high concentration of neutral reactive species, in particular O atoms. The species interact with solid materials causing surface functionalization, removal or organic impurities, nanostructuring of polymers, selective etching of polymer composites or synthesis of metal-oxide nanoparticles. The flux of O atoms onto the surface-facing plasma is often between 1020 and 1023 m−2 s−1. While the physical interaction with solid materials (i.e. heterogeneous surface recombination) does not depend much on the sample temperature, the chemical interactions (functionalization, etching, oxidation) increase significantly with increasing temperature. The key treatment parameters are therefore the fluence of O atoms onto the sample surface and its temperature. The recommended ranges of parameters for various technologies are shown in the graphical abstract.