We present an optical investigation of GaN pillars using both micro-Raman (mu-Raman) and microphotoluminescence (mu-PL) spectroscopy. GaN pillars of diameter ranging from 100 nm to 5 mum were fabricated by electron beam lithography and reactive ion etching (RIE) with SiCl4 plasma. Optical measurements of both mu-Raman and mu-PL on individual pillars show consistent variations in the properties of the fabricated GaN structures as a function of GaN pillar size. mu-PL mapping gives strong evidence for defect-induced donors and/or acceptors near the facets of the RIE etched pillars. RIE for the nanostructuration of GaN could be used in the future to allow spectroscopic studies of a few or single quantum objects such as GaN quantum dots. (C) 2002 American Institute of Physics.