Plasma etching was applied for removal of the amorphous carbon layer that covers aligned carbon nanotube films produced by pyrolysis of metal-containing organometallic precursors. Microscopic and kinetic studies showed that amorphous carbon could be easily removed by H2O-plasma etching while carbon nanotubes remain largely unchanged under relatively mild plasma conditions. Prolonged plasma treatment, however, was found to cause a controllable disintegration of the graphitic structure, leading to a region-selective opening of the aligned carbon nanotubes (e.g., the removal of one end-cap only). Metal-filling was demonstrated to be also possible even with the resultant one-end opened nanotubes.