The structural, magnetic and transport properties of La2/3Sr1/3MnO3 thin films, prepared by laser ablation on LiNbO3 substrates, have been characterized for different temperatures and applied magnetic fields. The deposited films have grown highly oriented, with a (111) preferred growth direction. Their lattice parameter was a = 3.86 Å. From the temperature dependence of the magnetization and of the electrical resistivity their Curie (TC) and metal-insulator (TMI) transition temperatures were determined (TC ~ 360 K, TMI ~ 260 K). Spin-dependent tunnelling across grain boundaries was found to dominate the behaviour of the transport properties of the La2/3Sr1/3MnO3 thin films, on the studied temperature region.