Polarized absorption and fluorescence spectra of columnar liquid crystals formed by triaryl pyrylium salts are reported. The great Stokes shift and the time-resolved evolution of the fluorescence observed following laser excitation are interpreted by means of a theoretical model. based on the excitonic theory and quantum chemistry. The results concerning the energetic topography (excitation energy as a function of the position of the excited chromophore) and the simulated fluorescence spectra of columnar aggregates are reported. The influence of orientational defects on the photophysical properties is investigated. According to this model, absorption corresponds to coherent excitation while fluorescence may arise either from collective excited states or from localized ones related to defects.