This article reports on interrelationships between x-ray structure, mechanical properties, coefficient of friction mu, and wear coefficient k of similar to 3000 m thick nc-TiC/a-C nanocomposite films sputtered using unbalanced magnetron from a composed C/Ti target (empty set = 100 mm); here nc and a denotes the nanocrystalline and amorphous phase, respectively. It is shown that (1) mu and k of the nc-TiC/a-C nanocomposite film strongly depend not only on its hardness H but also on its effective Young's modulus E*=E/(1-nu(2)); here nu is the Poisson s ratio, (2) the nc-TiC/a-C nanocomposite films with C/Ti > 1.5 and the ratio H-3/E*(2) (characterizing the resistance of film to plastic deformation) ranging from similar to 0.2 to similar to 0.3 exhibit the lowest values of mu and k, and (3) mu increases with increasing load L of the testing ball. The main result of this investigation is the finding that the achievement of the lowest value E* at a given value of H is of key importance in the formation of films with the lowest values of coefficient of friction mu and wear coefficient k. (C) 2010 American Vacuum Society. [DOI: 10.1116/1.3294717]