Photoluntinescence (PL) properties of various Ge-based nanostructured materials, prepared using methods such as chemical etching, ion implantation and spark processing, have been studied. The PL was much stronger from the samples containing Ge nanocrystals, in comparison with their counterparts with no or less Ge nanoparticles, hinting at the likely role of the quantum confinement in Ge nanocrystals (NCs) in the light emission process. On the other hand, defects in the oxides or Ge-O bonded material alone are also shown to emit light in the same energy zone as with the Ge NCs. Discussion on these results is presented. (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.