In the present work the formation of water complexes with ionic liquids (ILs) -1-butyl-3-methylimidazolium chloride [bmim][Cl] and 1-butyl-3-methylimidazolium tetrafluoroborate [bmim][BF 4 ] in KBr matrix at ambient temperature by IR technique was studied. There was shown that between the components of the system the hydrogen bond, in which the heteroaromatic fragment and anion (Cl À or BF 4 À ) can participate, arises. The ab initio calculation in terms of DFT predicts a possibility of an interaction between the hydrogen atoms of CH bond in heteroaromatic ring and CH 3 -group with oxygen atom as well as between anion (Cl À or BF 4 À ) with hydrogen atom of water molecule.