The composition, the structure, and some physical properties of boron–carbon–nitrogen solid solutions prepared by chemical vapor deposition (CVD) have been investigated. Both crystalline films and amorphous granular materials resulting respectively from heterogeneous and homogeneous nucleation were characterized by X‐ray diffraction, XPS, RBS, and TEM. The compositions of these single‐phase materials are gathered in two main domains located in the B/N>1 part of the C─B─N composition diagram. It is stated that the carbon‐rich domain results from structural disorder of an ideal C5B2N composition. The thermal behavior of these films indicates that no mass loss can be detected after 1 h at 1700°C but a graphitization and a formation of small amounts of B13C2are observed. Density and preliminary electrical conductivity measurements were