The three dimensional photonic crystals concept has been employed for photocatalysis. Slow photons observed in photonic crystal structures will enhance the absorption of materials when the photon energy matches the absorbance of the materials, which would improve the photocatalytic efficiency. In this work, three dimensionally ordered macroporous (3DOM) titania was prepared by applying the colloidal templating method with a range of pore diameters. Calcination at different temperatures to remove the templates resulted in different crystalline phases. The structural and photonic properties were characterized and their effects on photocatalytic activity are presented as well. A strong effect of the pore diameter on the photocatalytic activity was observed and correlated with the photon energy involved in the photodegradation process of organics. A very interesting phenomenon was also observed: the sample prepared by using PS spheres of 250 nm had a high photocatalytic efficiency, which mismatched the effect of pore diameter, probably owing to the slow photon effect.