The changes in crystallites size, phase composition, morphology, sorption and photocatalytic properties of TiO2 (Degussa P-25) as a result of mechanoactivation in planetary ball mill Pulverisette 5 are reported. These alterations are investigated as a function of the times of milling and storage before the photochemical test, the nature of triboreactor material (agate or steel) and the activation mode (in air or as methanol suspension). Malachite green and methylene blue solutions are used as model pollutants in the photocatalytic tests. The energy stored in the powder after milling is calculated. Decrease of the size of crystallites and morphological grains, small increase of the anatase relative content (at activation in air), a significant increase of the TiO2 sorption ability (especially after mechanoactivation in steel vessels) without substantial changes in the photocatalytic activity and an increase of the photocatalytic effectiveness after mechanoactivation in agate vessel at certain conditions are observed. (C) 2008 Elsevier B.V. All rights reserved.