Catalytic hydrogen production from renewables is a promising method for providing energy carriers in the near future. Photocatalysts capable of promoting this reaction are often composed of noble metal nanoparticles deposited on a semiconductor. The most promising semiconductor at present is TiO2. The successful design of these catalysts relies on a thorough understanding of the role of the noble metal particle size and the TiO2 polymorph. Here we demonstrate that Au particles in the size range 3–30 nm on TiO2 are very active in hydrogen production from ethanol. It was found that Au particles of similar size on anatase nanoparticles delivered a rate two orders of magnitude higher than that recorded for Au on rutile nanoparticles. Surprisingly, it was also found that Au particle size does not affect the photoreaction rate over the 3–12 nm range. The high hydrogen yield observed makes these catalysts promising materials for solar conversion.