Molecular hydrogen endohedrally confined using H-2n-fullerene-like cavities is investigated with resort to density functional theory. Firstly, the pressure dependence of the ground state energy and internuclear distance of a single H-2 molecule is obtained as a function of a H-20 cage volume. Secondly, 30 hydrogen atoms are allowed to relax under the confinement of a H-60 cage of radius R similar to 4 Angstrom to reach a configuration of minimum energy. Hydrogen molecules form and self-assemble into a (H-2)(15) stable cluster characterized by two coaxial sixfold symmetry ring structures. The present confinement model gives results in agreement with experimental observations. (C) 2004 Published by Elsevier B.V.