Three-dimensional (3-D) titanium dioxide (TiO2) nanoforests with a large surface area and a high electron transport property have been successfully synthesized on transparent conducting oxide (TCO) substrate by using a unique multi-step hydrothermal synthesizing process. First, TiO2 nanorods with well-controlled density and length are grown on TCO glass substrate. TiO2 nanowires are then synthesized on TiO2 nanorods with another hydrothermal process. In comparison with previously reported one-dimensional (1-D) TiO2 nanorod arrays. TiO2 nanoforests offer a larger surface area for the same height, which is beneficial for achieving higher efficiency dye-sensitized solar cell (DSSC). The experimental results confirm that a conversion efficiency of 3.93% can be achieved with a 5.1 mu m long TiO2 nanoforest based DSSC under AM 1.5 illumination. (C) 2012 Elsevier B.V. All rights reserved.