Hydrogenated amorphous carbon films have been prepared from plasma-enhanced chemical vapor deposition. Both the as-deposited films and those thermally annealed for two hours at 300 °C exhibited insulating characteristics. Neither a thermally activated process nor a hopping mechanism was observed for the conductivity. An increase occurred in the conductivity by an order of five after two hours of subsequent treatment under Ar plasma for both the as-deposited and thermally annealed films. In addition, thermally activated conductivity with an activation energy of around 0.3 eV was observed.