The electronic properties of functionalised single and multi wall carbon nanotubes (SWNTs and MWNTs, respectively) were investigated in depth by conventional electrochemical techniques in solution. Significant differences were observed between these two classes of carbon nanotubes. In fact, despite functionalisation strongly modified the electronic properties of carbon nanotubes, the enrichment of the density of states of MWNTs with respect to SWNTs, due to larger tube diameters, is still appreciated. In addition, the redox behaviour of the MWNTs shows a series of discrete single electron-transfer events (a coulomb staircase), which are undetected in the case of SWNTs. This quantised capacitance charging phenomena is analogous to that observed for other nanosystems which is attributed to the discrete charging of conducting core, coated with a dielectric film in an electrolyte solution. (C) 2007 Elsevier Ltd. All rights reserved.