We investigate conformation-specific UV spectra of benzo-18-crown-6 complexes with a potassium cation using a UV-UV hole burning (HB) technique developed for ions in a quadrupole ion trap. Three different UV-UV HB spectra are obtained: two spectra represent the electronic spectra of conformers, K-a and K-b, respectively, and the third exhibits the transitions of a vibrationally 'hot' K-b conformer. These demonstrate that the UV-UV HB technique, of which the applicability was first tested only for ions of a single isomer, can be used to differentiate vibronic peaks of ions existing as two or more different conformers including their vibrationally 'hot' species. (C) 2014 Elsevier B. V. All rights reserved.