This presentation discusses recent progress in the development of structural composites with added functions, such as sensing and energy storing capabilities. The strategy used consists in producing hierarchical composites that contain carbon fibre and fibres of carbon nanotubes. The talk first presents progress in hierarchical composites with single functions. As an example, we present results on the integration of CNT fibre interleaves between CF fabric to improve interlaminar properties. Mode-I test results indicate improvement with respect to control samples and highlight the importance of fabrication in obtaining defect-free samples that thus exploit the presence of the tough interleaf. Next, the talk presents results on using CNT yarns as sensors to monitor composite fabrication and deformation once in the cured state. The chemical sensing capability arises from polymers acting as electron dopants of the CNT yarns, whereas stress sensing is due to the intrinsic piezoreistance in the nanostructured fibres. Finally, basic electrochemical properties of CNT fibre-based supercapacitors with solid electrolytes consisting of a thermoplastic and an ionic liquid. These devices are shown to be flexible and to have specific tensile above that of copper.