Transition metal nitrides such as TiN and VN belong to the class of refractory hard metal nitrides with unique physical and chemical properties. Due to high melting points, ultra hardness, good electrical and thermal conductivity, and slow resistance to corrosion these compounds are widely used in many applications. Also these compounds are applied as the counterparts of modern functional composite materials. Here we present the results of comparative study of TiN and VN interaction at mechanochemical processing of the equimolar TiN-VN mixture in a high-energy planetary mill and after HPHT sintering (7.7 GPa and 1750-2300 °C) of the cBN-TiN-VN charge, which contains 35 vol. % of this mixture. It was found that mechanical alloying for five hours or HPHT sintering at 2000-2300 °C results in the formation of two Ti_xV_1-xN_y and V_xTi_1-xN_y mutual solid solutions containing 8-10 at.% of vanadium or titanium, respectively in the samples studied. The crystal structures of solid solutions formed at mechanical alloying is characterized by increased value of defectiveness of their metal sublattices, while HPHT sintering leads to rearrangement of the nitrogen atoms in crystal lattice. It was shown that the preliminary processing of initial powder mixture in a ball mill promotes the occurrence of solid state reactions at HPHT sintering of composites containing a mixture of TiN and VN nitrides and influences their physical characteristics.