Titanium dioxide photonic crystals (PCs) were obtained using the sol-gel method and polystyrene (PS) micro-spheres as a template with two different diameters: 300 nm and 460 nm. The resulting materials were labeled as PC-300 and PC-460. In the following step, PCs were modified with silver nanoparticles (AgNPs) generated by the photoreduction of silver Ag+ ions. The obtained PCs were denoted as AgNPs/PC-300 and AgNPs/PC-460. The size of the AgNPs were 28 nm +/- 2 nm for the AgNPs/PC-300 and 21 nm +/- 1 nm for AgNPs/PC-460. The characteristic features of TiO2 PCs, such as electronic band gap (BG), photonic band gap (PBG) and an occurrence of slow photon effect (SPE), were determined with the use of UV-vis spectroscopy. The photocatalytic performance of the prepared PCs was defined by monitoring the photodegradation rates of Rhodamine B (RhB) measured in the presence of PC-300, PC-460, AgNPs/PC-300, AgNPs/PC-460 and non-porous TiO2 coating (NPC) as reference material. It was found that the appropriate utilization of SPE by overlapping the edge of PBG with semiconductor BG and electron trapping by the presence of AgNPs exerted a strong synergistic effect on the photocatalytic properties of AgNPs/PCs.