The underlying vibronic structure of methyl-substituted ladder-type poly(para-phenylene) absorption and emission was investigated using temperature dependent fluorescence and site-selective fluorescence spectroscopy. Principal contributions in the vibronic manifold were identified from modelling of the data, and were found to be in good agreement with theoretical predictions after a re-evaluation of the position of the zero-phonon transition. A crossover to Raman dominated spectra at low excitation energy and temperature was observed. The influence of Raman effects should form an important point of consideration in the interpretation of fluorescence data. (C) 2009 Elsevier B. V. All rights reserved.