Carbon nitride thin films deposited by reactive RF magnetron sputtering were studied to obtain knowledge for various applications. Different types of analyses were performed on CNx layers to determine both surface and bulk properties of the films and particular attention was paid to nitrogen incorporation in the films. The variation in composition and type of chemical bonds between atoms in the films was followed using X-ray photoelectron spectroscopy (XPS). The results showed that the N/C ratio reaches 0.7. The wettability tests can lead to the determination of superficial energy, providing very interesting information about biocompatibility. The wettability and superficial energy decreased with nitrogen content. The evolution of the elastic properties of the CNx layers as a function of the nitrogen incorporation was investigated by Brillouin spectroscopy. The measured Rayleigh wave velocity decreased with nitrogen incorporation.