Potassium and tetraphenylphosphonium salts of novel aryldithiofluorophosphonic acids were synthesized. Lawesson's Reagent was allowed to react with KF in acetonitrile to yield the potassium salt of p-methoxyphenyldithiofluorophosphonic acid. Treatment of the latter with tetraphenylphosphonium chloride resulted in the formation of the tetraphenylphosphonium salt. The structures of the compounds were elucidated by FTIR, H-1, C-13, F-19, and P-31 NMR spectroscopy as well as by ESI-mass spectrometry. The molecular and crystal structure of the tetraphenylphosphonium salt, determined by single crystal X-ray diffraction, is also presented.