Experimental and theoretical approaches are used to determine hydrogen storage mechanisms in nanopores of multiwalled carbon nitride nanotubes (MWCNNTs). First, the authors produce similar to 0.6 nm pores on the stems of MWCNNTs by plasma-enhanced chemical vapor deposition. Next, thermal desorption spectra were measured and obtained two different peaks. This is explained by hydrogen desorption barriers of 0.36-0.50 eV attributed to two different types of similar to 0.6 nm pores. Moreover, H-2 adsorption between complete interlayers is found to be endothermic by 1.27 eV. In this respect, open channels and similar to 0.6 nm pores on MWCNNTs are considered to provide the route for reversible hydrogen storage. (c) 2006 American Institute of Physics.