Pulsed laser induced breakdown of a titanium target in water medium is carried out to synthesize TiOx (x = 1.51, 2) nanoparticles. The focusing condition of the source laser was varied and its potential effect onto the size and structural phases of the nanoparticles are reported. Under tightly focused condition, high temperature and high pressure plasma led to formation of rutile TiO2 whereas at regions of low pressure and low temperature plasma, anatase TiO2 was formed. In addition, oxygen deficient TiO1.51 was also formed for all the focusing condition due to the transient plasma quenching induced by pulsed source laser. Some studies onto the optical properties of the colloidal solution containing TiOx nanoparticles are also performed. (C) 2010 Elsevier B.V. All rights reserved.