Poly-(3,4-ethylenedioxythiophene) (PEDOT) with a unique three dimensional (3D), macroporous structure (3D-P-PEDOT) was prepared by a facile electrodeposited approach in a mixed solvent of CH2Cl2 and water. The 3D-P-PEDOT was characterized by SEM, EDS, Raman and electrochemical methods. The addition of water has significant influence on the morphology of PEDOT. 3D-P-PEDOT composed of micrometer sized craters and bumps decorated with nanometer sized fibrous structures was prepared in the presence of more than 200 mu L water at applied potential of 1.3-1.6 V within one minute. However, this unique structure cannot be produced in pure CH2Cl2 or pure water solution. The effects of dosage of EDOT and deposition potential on the morphology of PEDOT were also investigated. The possible growth mechanism of this 3D-P-PEDOT was discussed. Finally, this unique 3D-P-PEDOT was used to detect nitrite and ascorbic acid respectively, and higher sensitivity, wider linear range and lower over-potential were obtained than those of previously reported PEDOT based sensors. Our method may provide an efficient approach to fabricate conducting polymer material with new micro-nanostructures, advanced properties and great potentials in various electrochemical fields. (C) 2014 Elsevier Ltd. All rights reserved.