We are presenting recent advances in surface functionalization of materials such as functional polymers using gaseous plasma treatments. Functionalization is a result of chemical interaction between solid materials and reactive plasma species including charged particles, neutral radicals, excited species and UV radiation. The degree of surface functionalization depends on the type of polymers and fluxes of reactive plasma species. An appropriate choice of plasma parameters thus enables almost arbitrary tailoring of the surface wettability. This review paper gives a brief introduction to the formation of reactive gaseous species upon plasma conditions in different discharge configurations and describes plasma-surface interaction with an emphasis on the differences between different reactive plasma species. Analysis of the relevant literature is given and correlations between treatment parameters and surface finish are drawn. Numerous authors have used plasma treatment for modification of the surface functionalities, however, the obtained surface properties often differ even for the same materials. The reason for such diverse results is the application of various gaseous discharges for plasma generation. Apart from the type and amount of functional groups induced by plasma treatment, the surface functionality depends also on the surface morphology on the sub-micron scale; therefore, this effect is stressed as well. Finally, some future guidelines are given.