Carbon nanotubes (CNTs) were grown on Si substrates by rf CH4 plasma-enhanced chemical vapor deposition in a pressure range of 1–10 Torr, and then characterized by scanning electron microscopy. At 1 Torr, the CNTs continued growing up to 60 min, while their height at 4 Torr had leveled off at 20 min. CNTs hardly grew at 10 Torr and amorphous carbon was deposited instead. CH4 plasma was simulated using a one-dimensional fluid model to evaluate the production and transport of radicals, ions, and nonradical neutrals. The amount of simulated carbon supplied to the electrode surface via the flux of radicals and ions such as CH3, C2H5, and C2H was consistent with estimations from experimental results.