We have fabricated front-side illuminated dye-sensitized solar cells (DSSCs) with a thin film of vertically oriented TiO2 nanotubes used as the negative electrode. The TiO2 nanotube film was formed by anodizing a metallic titanium thin film that was deposited on a transparent conductive oxide (TCO) layer with an intermediate, protective TiO2 layer. We characterized the structural and electronic properties of the formed TiO2 nanotube films. Titanium tetrachloride (TiCl4) treatment was applied on the TiO2 nanotube film to improve the performance of the DSSCs. We have investigated effects of TiCl4 treatment on the solar cell parameters of the DSSCs: short-circuit current density (ISC), open-circuit voltage (Voc), ideal factor (n), series resistance (Rs) and shunt resistance (Rsh). The parameters have been derived by analyzing measured I-V characteristic of the DSSCs on the basis of the method we have previously proposed. We demonstrate that the performance of the DSSCs is improved by TiCl4 treatment. We discuss the effects of TiCl4 treatment on the performance on the basis of the derived cell parameters.