A sensor electrode was modified by multi-walled carbon nanotubes functionalized by dithizone. The electrode was used for determination of trace amounts of cadmium (II) ions. The electrode composition was 67% graphite powder, paraffin 23%, 10% modified MWCNTs (W/W). The linear range for lead (II) was 1.8×10^-7 to 1.0×10^-4 mol L^−1and the limit of detection was obtained1.0×10^−7 mol L^−1. The lifetime of the electrode was 12 weeks and a fast response time was observed. The electrode was used for determination of trace amounts of Cd(II) ions in standard reference materials of water and soil.