Nanocavities created in silicon using high energy He+ implantation are studied using the combination of transmission electron microscopy experiments and small-angle X-ray scattering measurements. The complementarity of the two techniques is presented and using the results from both techniques, a complete characterisation of nanocavities can be drawn in terms of location of the implanted region, morphology. mean size and volume fraction as well as the cavity size distribution. (C) 2009 Elsevier B.V. All rights reserved.