[en] TiO_2-based nanowires were prepared by a hydrothermal method, and Pt nanoparticles were deposited on the nanowires by atomic layer deposition (ALD). The size and loading of Pt nanoparticles with very good uniformity could be controlled by the ALD cycle number, along with acid or water treatment of the nanowires. The lower growth rate and the loading of Pt nanoparticles were obtained with water treatment. With acid treatment, the growth rate and loading were increased, and this increase was attributed to the formation of higher density of hydroxide groups on the nanowires. The photocatalytic activities of Pt-deposited nanowires were investigated. The deposition of Pt on the nanowires resulted in both enhanced light absorption in the visible region and electron–hole separation efficiency. The water-treated nanowires exhibited the highest degradation rate of rhodamine B and the highest hydrogen evolution rate. A maximum amount of hydrogen evolution, 13.8 mmol g"−"1 in 6 h, was achieved. (paper)