A comparative study of the deposition of diamond-like carbon films using methane or benzene in a microwave electron cyclotron resonance plasma-enhanced chemical vapor deposition system has been performed. Process variables studied were reactor pressure, applied radio frequency substrate bias, and microwave power. The plasma stream was characterized using optical emission spectroscopy and mass spectrometry. Film properties studied included optical energy gap, total hydrogen content, integrated C-H stretch absorption, index of refraction, and Raman spectra. The use of a high C/H ratio reactant such as benzene was found to be advantageous over methane in that higher deposition rates were possible and the resultant films exhibit diamond-like properties without the application of large substrate biases. Another result of this investigation was further confirmation that hard carbon films contain a significant quantity of nonbonded hydrogen [A. Grill and V. Patel, Appl. Phys. Lett. 60 (17), 2089 (1992)].