In the present study, we investigated the effects of annealing of amorphous hydrogenated carbon (a-C:H) films, particularly with respect to structural changes of the carbon network and their impact on the hydrogen-atom-induced erosion. The a-C:H films were deposited at 300 K on a Pt(111) single crystal using the ion-beam deposition (IBD) method. Electron energy loss spectroscopy (EELS) and high-resolution electron energy loss spectroscopy (HREELS) were employed to monitor structural changes of the carbon network as a function of the annealing temperature. A transition from an sp(3)-rich carbon network toward an sp(2) dominated, "graphitic" structure was observed around 900 K. The hydrogen-induced erosion of as-deposited and annealed a-C:H films was investigated by in situ mass spectrometry. The postdeposition annealing did not change the overall erosion rates of a-C:H films; however, the product distribution indicates the growth of existing graphitic structures as a consequence of annealing at temperatures above 900 K.