The effect of TiO2 particles on the yield of H-2 formation under water radiolysis is measured. Irradiations were performed using a Co-60 gamma-ray source as well as with He ions particles (4He2(+)) generated by a cyclotron with an external beam energy of 6 MeV. The resulting hydrogen as a stable product of radiolysis was measured by mass spectrometry. G(H-2) obtained for water radiolysis by He ions-irradiation in aerated and argon water are found to be 1.91 x 10(-7) and 1.35 x 10(-7) mol J(-1), respectively. In the presence of titanium oxide anatase-type dispersed in water, under He ions-irradiation, G(H-2) is found to increase slightly from 1.04 x 10(-7) to 1.35 x 10(-7) mol J(-1) by increasing the specific surface from 8 to 253 m(2)/g, respectively. Under gamma-irradiation, G(H-2) is found to be 0.41 x 10(-7) mol J(-1) close to primary yield of hydrogen in presence of OH. Radical scavenger. In addition, radiolysis of water adsorbed in the titanium oxide with low water content, which corresponds to a few layers of water sorbed onto the solid surface gives a huge values of the G(H-2). For the same amount of water, with using the dose absorbed by TiO2 particles, for He ions-irradiation, G(H-2) increases from 14.5 x 10(-7) to 35 x 10(-7) mol J(-1) by increasing the surface area of TiO2 nanoparticles from 4 to 52 m(2)/g, respectively. For gamma-irradiation G(H-2) is found to be 5.25 x 10(-7) mol J(-1) for the sample with 8 m(2)/g specific surface area. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.