The resistance of ion implanted surfaces against wear and corrosion is influenced by the chemical composition of the modified zone. It is shown that glow discharge optical spectroscopy (GDOS) is a sensitive and easily applicable technique to investigate composition depth profiles of implanted layers. Despite the layer thickness of less than 1 mu m a good resolution can be realized by using polished sample surfaces and suitable analyzing parameters. Results of carbon and nitrogen implantations in various doses into high speed steel, pure titanium, Ti-6Al-4V and physical vapor deposited (PVD) titanium nitride coatings are presented. Substantial differences in the depth profiles were found for carbon and nitro en implantations into M2 steel and into TiN coatings. Carbon implantations show almost Gaussian-like carbon depth distributions with increasing maximum concentration corresponding to higher implantation doses. However, the amount of nitrogen which can be incorporated by ion implantation into TiN coatings was found to be limited and an almost uniform saturation concentration within the implanted zone was detected.