In the presence of Et3N-5HF electrolyte, anodic fluorination of 2,6-di-tert-butylphenols with or without a substituent X (halogen) at its para-position (la-c) successfully afforded 4,4-difluoro-2,6-di-tert-butylcyclohexa-2,5-diene-1-one (2), which was readily converted to 4-fluoro-2,6-di-tert-butylphenol (3) in good yields by the subsequent reduction with Zn in acidic aqueous solutions. We revealed some novel information on the electrochemical oxidative fluorination mechanism of 1a-c, which is well supported by the product distribution curve and the cyclic voltammogram of the possible oxidative products, as well as that of la in Et3N-5HF.