Amorphous hydrogenated carbon thin films have been deposited from benzene vapor in an electron cyclotron resonance plasma-enhanced chemical vapor deposition reactor. The effects of gas flow rate, pressure, and microwave power on deposition rates, chemical structure and composition, and on film density were investigated. Plasma enhanced dissociation and ionization reactions were monitored by mass spectrometry and by optical emission spectroscopy. Dissociation products included a variety of unsaturated hydrocarbon species (primarily ethylene) and hydrogen. Deposited films were characterized by Fourier transform infrared spectroscopy, Raman spectroscopy, and fluorescence spectroscopy. Films displayed a condensed, aromatic, hydrocarbon-like structure, albeit without extensive conjugation. Possible reaction sequences leading to the observed film structures have been proposed.