4-(Ferrocenylmethylidene)-4H-cyclopenta[2,1-b:3,4-b']-dithiophene was electropolymerised both on indium-tin oxide and interdigitated gold electrodes. The optical and electrical characteristics of the polymer (PCPBTFC) were studied as a function of storage time and relative humidity. PCPBTFC showed both electronic and redox conductance and, in the presence of humidity, it also showed the ionic conductance due to ions formation inside the material. The spectrum and conductance evolution over time indicated that PCPBTFC underwent decomposition in the presence of oxygen and water, consequently, its performance as sensitive material for humidity sensors decayed. (c) 2006 Elsevier Ltd. All rights reserved.