Ultra-fine grained copper prepared by high pressure torsion has been studied by means of slow positron implantation spectroscopy with Doppler broadening measurement. In addition, conventional positron lifetime and Doppler broadening spectroscopy have been utilised. Defects present in the specimens were identified, their spatial distribution and depth profile have been determined. The results are discussed in correlation with those obtained by XRD and TEM. (C) 2002 Elsevier Science B.V. All rights reserved.