Abstract: Thioether and aromatic molecules were electrochemically radiolabeled with [18F]Fluoride under carrier-added and no-carrier-added conditions. The addition of excess carrier fluoride (i.e. stable isotope fluoride) in traditional electrochemical fluorination leads to low fluorination yields, which cause low radiochemical yields and molar activity when using [18F]Fluoride. Electrochemical syntheses were extensively investigated herein and optimized to remove the need for the addition of excess carrier fluoride, increasing radiochemical yield and molar activity rendering this electrochemical methodology suitable for the potential use in Positron Emission Tomography radiotracer synthesis. The electrochemical fluorination mechanisms of ECEC, where E is an electrochemical process and C is a chemical reaction, and fluoro-Pummerer rearrangement were explored with the transition to no-carrier-added conditions. New electrochemical fluorination methods and novel reaction conditions were used to perform no-carrier-added 18F-radiolabeling of thioethers and aromatics with improved radiochemical yield and molar activity for use in the synthesis of radiotracers for Positron Emission Tomography.