Transparent electrodes, formed by 50 nm bundles of rutile nanowires (NW), 2 nm in diameter, have been prepared directly by chemical bath deposition at low temperature on conducting glass. The photoelectrocatalytic behavior of such NW electrodes has been studied in acidic solutions in the presence of model organic molecules (formic acid and methanol) and has been compared with that characteristic of thin films consisting of larger (20 Ă 40 nm) ellipsoidal rutile nanoparticles (NP). Both UVâvis absorption and photoaction spectra evidence that the NWs are in the quantum confinement (QC) regime, as the band gap is 0.27 eV larger than that of the ellipsoidal nanoparticles. From the onset of the accumulation region, determined by voltammetry, the conduction band edge is estimated to shift upward around 0.06 eV as a result of QC. In the presence of efficient hole acceptors, significantly larger photocurrents were observed for NW films than for NP electrodes. This indicates that the morphology of the film, together with the existence of QC and the particular surface structure of the wires, confers to the corresponding electrodes particularly good photoelectrocatalytic properties. A simple model based on the electron diffusion equation is applied to rationalize the observed photoelectrochemical behavior. The results point to an efficient hole transfer and, particularly, to a diminished electron recombination due to the absence of intergrain boundaries in NW electrodes as compared to NP electrodes. Complementarily, the reactivity of the photogenerated electrons was assessed through photopotential measurements, which also reflect an increased reactivity of electrons toward oxygen in the case of NW films.