Pt-, Au- and Ag-deposited Degussa P25 photocatalysts [at 1% (m/m) noble metal loading] were prepared in which the noble metals are most likely to be very finely dispersed on the surface of the TiO2 nanocrystals. Deposition of noble metals increased the photocatalytic efficiency (relative to the bare photocatalyst) in the decomposition of oxalic-and formic acid, while decreased it in phenol containing systems. In H-2-production, a very high quantum yield has been found for the Pt-TiO2 photocatalyst in the presence of oxalic and formic acids as sacrificial reagents, which opens the possibility for the economic use of industrial side products (e.g., oxalic- and formic acid) for photocatalytic H-2-production.