Fluorine substitution can have a major effect on the electronic spectra and sometimes on the ground electronic state conformations of organic compounds. In this work we investigate the effect of perfluorination on the resonance Raman spectra of the simple diene, hexafluorobutadiene where the preferred ground state geometry is believed to be skew s-cis. A detailed comparison of theory with experiment is possible and excellent agreement is observed. In an ongoing study, we investigate the effect of fluorination on the photodissociation dynamics of methyliodide by investigation of CF 3I. The activity of the CH 3 umbrella mode observed in the resonance Raman spectrum of CH 3I obtained in resonance with the dissociative A state is attributed to a change in the geometry from pyramidal to planar as the C-I bond elongates. This should not be observed in the case of CF 3I since CF 3 is pyramidal. The consequences of this fluorine effect on the photodissociation product as revealed in the resonance Raman spectrum are investigated.