Carbon and nitrogen co-doped titanium dioxide nanotubes (C-N co-doped TiO2 NTs) catalysts were successfully synthesized using a hydrothermal method at N:Ti molar ratios between 0.1 and 1.0. Transmission electron microscope (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR), X-ray photoelectron spectroscope (XPS), UV-Vis diffuse reflectance spectroscope (UV-Vis DRS) and surface area analyzer were used to characterize the synthesized catalysts. Urea doping at N:Ti = 0.3 led to the highest sonocatalytic activity with an apparent-first-order rate constant of 0.0226 min(-1) as compared to 0.0098 min(-1) for the un-doped TiO2 NTs. The high performance was associated with the synergistic effects between the doped C and N atoms, higher surface area and lower band gap energy. It was also ascribed to the creation of surface oxygen vacancies due to the formation of Ti3+ species and better crystallinity of anatase phase as compared to the un-doped TiO2 NTs. Most of the nitrogen atoms were bonded to oxygen atoms in the interstitial sites (Ti-O-N and Ti-N-O), but only minority of them could substitute the sites of oxygen atoms (N-Ti-O). C atoms evidently presented in the form of Ti-C and a complex carbonate species on the catalyst surface. (C) 2012 Elsevier B.V. All rights reserved.