The NiTi coatings studied here are deposited using ion sputtering technique. The target consists of Ni0.49Ti0.51 and the sputtering ions are reactive nitrogen N+ or inert argon Ar+, or a mixture of both argon and nitrogen ions. In this paper, we relate the tribological properties of these thin films to their microstructure, for different experimental preparation conditions. The structure of the sputtered coatings are characterised by X-Ray Diffraction (XRD) and mainly by Extended X-Ray Absorption Fine Structure (EXAFS). The results reveal that chemical affinity between titanium and nitrogen largely dominates the other phenomena and that coatings are composed of TiN crystalline particles, embedded in an amorphous matrix. It is shown that the wear improvement depends on the size of the precipitates and also on the composition of amorphous matrix. Best tribological results are obtained with an amorphous NixN1-x matrix type with x close to 0.75.