Atomic layer deposition (ALD) of titanium dioxide from TiCl4 and H2O was studied at substrate temperatures of 100-400 degreesC. Using a real-time quartz crystal microbalance method, it was demonstrated that although the surface reactions were self-limited, the growth rate depended on the temperature and development of the thin film structure. Relatively low growth rate which was obtained in the TiCl4/H2O ALD process, was found to be a result of a significant chlorine amount adsorbed during the TiCl4 pulse. Surface intermediates formed in the initial stage of TiCl4 adsorption were unstable and weakly bonded to the surface. Desorption and decomposition of these species additionally influenced the deposition late and, especially, its dependence on the precursor pulse times.