The photocurrent generation of poly(3,4-ethylenedioxythiophene) (PEDOT) grown on TiO2 nanoparticles were examined. PEDOT was deposited on the surface of mesoporous TiO2 nanoparticle by chemical polymerization of 3,4-ethylenedioxythiophene (EDOT) under oxidative condition, to afford blue colored conductive particles, having average diameter of 80 nm when the feed ratio between TiO2 and EDOT was 1:1.5 by weight. A photoelectrode coated with the PEDOT-on-TiO2 nanoparticles showed much higher photocurrent generation for a redox couple of hydroqunone and quinone, compared to that of PEDOT or TiO2 only. The photoelectrode prepared from PEDOT-on-TiO2 nanoparticles (ratio 1/2) showed photocurrent higher than 2.8 mu A/cm(2) upon excitation with UV light under an external potential of -0.4 V (versus Ag/AgCl). The current generation and photoswitching properties was maximized when the feed ratio between TiO2 and PEDOT was 1:2.