The second ionization energy of beta-picoline was determined from photoionization experiments as (2)IE(beta) = (24.05 +/- 0.1) eV and the threshold for the dehydrogenation of the dication generated by photoionization as AE(-H(2))(beta) = (25.0 +/- 0.2) eV. The second ionization energy is about 0.5 eV lower than values recently determined for alpha- and gamma-picoline, whereas the energies required for dehydrogenation are similar. In order to rationalize the different behavior of dications generated from these isomeric picolines, we have performed a mass spectrometric investigation of the fragmentation patterns of the individual picoline dications and an extensive series of DFT calculations to explain the observed spectra. (C) 2011 Elsevier B.V. All rights reserved.