The TiN thin films were deposited by reactive magnetron method. The structure and chemical composition of films were determined by X-ray, EDX and electron microscopy investigations. These studies indicate a complex structure of as-sputtered films. The films are composed of an amorphous matrix that includes nanocrystallites of TiN and Ti2N. The amorphous as-sputtered films transform into crystalline films during thermal treatment above 673 K. Both electrical and optical properties of amorphous films differ substantially from those of crystalline films of the same chemical composition. Amorphous TiN films exhibit high electrical resistivity, high transmission of light in the visible range and a lack of metallic brilliance. The development of the structure models during thermal treatment has been proposed.