One bound state for the very weakly interacting complex of H-2 with one He atom is computed using a recently obtained, very accurate potential energy surface [A. I. Boothroyd and P. G. Martin, J. Chem. Phys. 119, 3187 (2003)] and employing a discrete variable representation expansion. The spatial features of this very diffused, "halo" state are analyzed and discussed for various isotopic variants of the title system. (C) 2005 American Institute of Physics.