Micro- and nanostructuring of a substrate by direct writing of the structures with a localized radical jet using the scanning probe principle is demonstrated. Electrically neutral radicals created in a downstream plasma discharge are pumped through a small nozzle and directed on to the substrate. Due to the small distance between the nozzle and surface of the workpiece, localized interaction is induced. Etched structures with 270 nm resolution produced by a nozzle with a diameter of 250 nm are presented. The etching rates achieved for micro- and nanostructuring are 200 nm/min in photoresist and 400 nm/min in silicon, respectively. It is shown experimentally that the resolution of the process is determined by the diameter of the nozzle, provided that the working distance is small, i.e., less than the diameter of the nozzle. Fundamentals for the development of a tool for direct structuring in the sub-100 nm range, including nanofabrication of a sub-100 nm nozzle, are presented in this work.