The photocatalytic oxidation of sucrose in the presence of dissolved Fe3+ and Ag+ ions in titanium dioxide suspensions under near-UV illumination has been investigated. The oxidation of sucrose to carbon dioxide was enhanced in the presence of these metal ions at low atom:atom percentage concentrations. An optimum metal ion loading was observed for both silver (2.0 atom%) and iron (1.0 atom%) ions. Beyond the optimum metal loading, the activity of silver-modified TiO2 particles was lowered. In the case of iron-modified TiO2, the activity of the catalyst (5.0 atom% Fe3+) was lower than that of bare TiO2. The role of metal ions in photocatalytic reactions is a function of the type of the metal and its concentration in the system. Different mechanisms are responsible for the effects of different metal ions added to titanium dioxide suspensions.