Carbon nanostructures have been synthesized using the chemical vapor deposition technique (CVD) on different catalysts, using ethylene, acetylene, or methane as the hydrocarbons. Morphological characterizations obtained using a scanning electron microscope (SEM) showed that the reaction products are carbon nanofibers (CNF) with an outer diameter that depends on the reaction conditions and nature of the reactants. Hydrogen uptake measurements, performed volumetrically in a Sievert-type installation, showed the quantity of desorbed hydrogen (for pressure intervals ranging from 1 to 100 bars) depends oil the synthesis conditions and the treatment preceding the hydrogen absorption process. For carbon nanotubes that were prepared according to literature guidelines and obtained from ethylene on a Ni:Cu catalyst, the amounts of absorbed hydrogen were less than 1% by weight.