A complete analysis of the proton magnetic resonance spectra of quinoline1and isoquinoline2,3allowed to obtain signs and accurate magnitudes of the1H-1H inter-ring coupling constants (HIRC). Since corresponding19F-19F inter-ring coupling constants (FIRC) in perfluoro-quinoline4and -isoquinoline5are available it was worthwhile to consider whether a correlation could be established between HIRC and FIRC. A correlation of this kind would be of obvious interest to a better understanding of the transmission mechanism of long-range19F-19F couplings.