H-1-NMR spectra of TiO2 photocatalysts consist of two peaks with line widths of 500 Hz and 18 kHz. The sharp peak was attributed to physisorbed water, while the broader one is considered to correspond to the less mobile bound water or surface OH group. On UV illumination both peaks disappeared. The admission of air leads to the recovery of both peaks to some extent but in a different spectral feature for the broad peak, reflecting the surface structural change on TiO2 by photo illumination.