The total reflection X-ray absorption fine structure (TR-XAFS) technique was applied to adsorbed films at the surface of aqueous solutions of 1-decyl-3-methylimidazolium bromide (DeMIMBr), 1-hexyl-3-methylimidazolium bromide (HMIMBr) and 1-hexyl-3-methylimidazolium tetrafluoroborate (HMIMBF₄) mixture, and dodecyltrimethylammonium bromide (DTABr) and dodecyltrimethylammonium tetrafluoroborate (DTABF₄) mixtures. The obtained χ spectra were expressed as linear combinations of two specific spectra corresponding to fully hydrated bromide ions (free-Br) and partially dehydrated bromide ions adsorbed to the hydrophilic groups of surfactant ions (bound-Br) at the surface. The proportions of free-and bound-Br ions were evaluated as a function of surface tension and surface composition of the surfactants. The relation between counterion distribution and miscibility of counterions at the solution surface was discussed and the importance of hydrogen bond formation between surfactant cation and counter anion was stressed.