Pure plastic films are often too permeable for many packaging applications. In these cases, the deposition of a thin functional layer can act as a barrier for gases and water vapour. Glassy, transparent coatings like SiOx have demonstrated their ability to provide good permeation protection but since they are brittle, handling damage can occur. The development of more flexible diffusion barrier layers is, therefore, needed. Thin hydrocarbon coatings were deposited onto plastic films by de magnetron sputtering processes carried out in non-pulsed and in bipolar, pulsed, operating modes. The influence of the process parameters such as power, pulse frequency, process gas, working pressure, and bias voltage on the properties of the coatings was studied systematically for optimization. The C:H-barrier layers are amorphous, and their stoichiometry varies between C1H0.2 and C1H0.2. Hydrocarbon layers inhibit oxygen gas permeation up to an improvement factor of about 120, without affecting the recyclability of the plastic films. Moreover, this barrier type widens the application field for transparent packaging due to its intrinsic flexibility.