In this paper, we discussed the potential of hydrogen adsorption by three types of carbon materials (GNF, SWNT and AC) in relation with their surface reactivity due to their nanometric pore dimension. We realized experimental studies of hydrogen adsorption measurements on a high accuracy gravimetric device up to 5 MPa on a series of chemically activated carbons and nanomaterials offering a wide range of porosities. Comparison with a very high pressure volumetric device up to 70 MPa is also given. We used in the mass balance, the material skeleton density determined at 700 K. Samples were characterized by Raman spectroscopy, XRD, TEM and BET methods. Material analysis correlation with macroscopic gas adsorption helps to the phenomenon interpretation at molecular scale. Although gas-solid interactions are weak; the adsorption sites are dense and their accessibility is an important point for optimizing gas uptake by increasing material porosity development. We discuss the limitations of the physical adsorption as a storage tool.