The influence of symmetry label on vibronic coupling and IVR was studied in cis and trans isomers of hydroquinone and p-dimethoxybenzene using dispersed fluorescence spectroscopy. It was found that the IVR behaviour is almost identical for hydroquinone isomers and very different for p-dimethoxybenzene isomers. From the vibronic spectroscopy and density of states calculations in the case of hydroquinone, it was inferred that there is no preferential coupling with the gerade modes. Extending this result to p-dimethoxybenzene, the observed isomer dependent IVR was attributed to the differences in the electronic structure of the isomers.