The effect of the insertion of a krypton atom in the C-H bond of acetylene and hydrogen cyanide in their electronic properties and as hydrogen bond acceptor and donor has been evaluated by means of ab initio calculations, up to MP2/6-311++G(2d,2p) level. The results indicate that the noble gas atom transfer part of its electrons to the rest of the molecule, increasing its ability as HB acceptor and decreasing the HB donor ones. (C) 2003 Elsevier B.V. All rights reserved.