Interaction energy decomposition was performed for a series of HCOOH...Rg complexes, where Rg is either argon or krypton, and the formic acid molecule has trans or cis conformation. The decomposition, performed within Symmetry-Adapted Perturbation Theory framework, shows that even if the stability of the complexes is due to significant dispersion contribution, the role of induction and exchange should not be neglected. One of the complexes, which is the lowest energy minimum found, is a 'hydrogen bond-like' structure which, with respect to other complexes, exhibits visible changes in the relations between the interaction energy terms, particularly - much more pronounced induction contribution. (c) 2005 Elsevier B.V. All rights reserved.