Abstract.  Today, plasma nanostructuring of materials plays important role in improvement of different sensors including catalytic, by expanding the limits of operation in various directions. Herein a review of catalytic sensors based on metal-oxide layer for measuring the concentration of atom radicals of parent molecules is presented. Catalytic sensors are small pieces of suitable materials allowing for in-situ determination of the atom concentration. Oxygen atoms are detected using materials that form oxide films with moderate or high binding energy such as nickel and niobium oxides. Best sensitivity for oxygen atoms is obtained using catalytic sensors with nanostructured surface, more precisely metal-oxide nanowire surfaces. In any case, the sensing capacity depends on the probability for heterogeneous surface recombination of atoms to stable molecules. The sensors measure the atom densities in a broad range from roughly 10^13 to 10^16 cm^-3, i.e. the ranges commonly found in material processing. Whereas new nanostructured surfaces expand the measurement detection range as well as add very interesting features to sensors, such as capacity to overcome radical overloads and temperature stresses. Several examples of application are presented and discussed.