Plasma activated chemical vapour deposition from two different metal organic precursors was used to prepare Fe-C:H films. From the deposition rates, the film composition, determined by X-ray induced photoelectron spectroscopy (XPS), and by the analysis of the plasma gas composition with quadrupole mass spectroscopy (QMS), conclusions are drawn about the fragmentation of the different precursors in the plasma and about the deposition mechanism. We found that the deposition strongly depends on the degree of fragmentation and the energy of the ions impinging onto the substrate. For ferrocene (Fe(C5H5)(2)), the films deposited at different bias potentials show a steplike change in the Nm composition which can be explained by assuming two different deposition mechanisms : (1) direct incorporation; and (2) deposition via an adsorption layer of small radicals. For the films deposited from cyclooctatetraen-iron-tricarbonyl (C8H8-Fe-(CO)(3)), the composition of the film is not changing with bias-potential which can be explained by a complete fragmentation of the precursor in the plasma.