Nanostructured anatase titanium dioxide (TiO2) was synthesized by hydrolysis of tetrabutyl titanate at low temperature, re‐disolution with nitric acid and subsequent precipitation and annealing at different temperatures. Raman spectroscopy has been used for determining the crystallite size of the samples, through analysis of the bandwidth and position of the strongest Eg mode (phonon confinement model) and the position of the low‐wavenumber band (acoustic‐phonon confinement). A reasonable agreement is found with the data obtained using X‐Ray diffraction and UV‐Vis spectroscopy, although the differences increase when the crystallite size increases. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)