Vickers hardness (H V ) was predicted using three modern theoretical models: (i) thermodynamic model based on thermodynamic properties and crystal structure; (ii) Lyakhov-Oganov model which considers crystal structure topology, covalent bonding strength, degree of ionicity and directionality; and (iii) Mazhnik-Oganov model which is based on elastic properties. The fracture toughness (K Ic ) was evaluated using Mazhnik-Oganov model . The results on hardness and other mechanical properties such as bulk (B), shear (G) and Young's (E) moduli, Poisson's ratio () and fracture toughness (K Ic ) are summarized in Table and compared with relevant data for diamond, cubic boron nitride and cubic C 3 N 4 . Although there is consistency between all three models, preference should be given to H V values obtained in the framework of thermodynamic model which shows surprising agreement with available experimental data in the case of superhard compounds of the B-C-N system .