Plasma diagnostics is a useful tool for the evaluation of the influence of plasma parameters on the physical properties of sputtered thin films. Ti-N was deposited by unbalanced magnetron sputtering at room temperature. The plasma parameters were determined by cylindrical Langmuir probe measurements. The deposition parameters were correlated with the plasma characteristics through the determination of the electron mean free path. The ion density was calculated according to the collisional Zakrzewski and Kopiczynski correction to the Laframboise model extended to a two-component gas. In order to evaluate the ion bombardment per condensing atom, the chemical composition and density of the deposited thin films were determined by accurate electron probe microanalysis. The calculations show how the action of ion-atom collisions on ion collection by the probe affects the evaluation of the ion bombardment.