Project Abstract As cannabis becomes legalized in regions around the country, developing effective treatments for Cannabis Use Disorder (CUD) becomes increasingly important. Transcranial Direct Current Stimulation (TDCS) holds promise as an augment to existing behavioral treatments. Based on recent work in internet gaming disorder by our team, enhancement of regulation skills through TDCS of the Dorso-lateral Prefrontal cortex (DLPFC) may constitute a helpful treatment for addictive behaviors. Pairing TDCS of the DLPFC with specific training in reappraisal may further help individuals regulate craving by enhancing effectiveness of training in the beneficial emotional regulation strategy of reappraisal. Thus, the goal of this work is to examine if neurostimulation paired with reappraisal training may enhance emotional regulation, resulting in a reduction of cannabis use coupled with change in EEG correlates of regulation. Sixty participants will be recruited and assigned to either receive real or sham TDCS alongside reappraisal training in 5 weekly single 20-minute sessions using a double-blind design. Cannabis use will be measured daily using ecological momentary assessment (EMA) for the duration of the month. Use of EMA technique will allow us to obtain detailed cannabis use information and determine any change in use patterns. Further, we will examine EEG correlates of regulation of craving, using the regulation of craving task, after TDCS at the first and final visit. Use of EEG during the regulation of craving task post-stimulation at baseline and post-treatment will allow us to determine if DLPFC stimulation results in enhancement of reappraisal coupled with both reduction in self-report of craving to cannabis images and changes in EEG correlates of regulatory control and reactivity while participants attempt to regulate their craving. We predict that real, as opposed to sham, TDCS will be associated with reduction in cannabis use as measured by EMA, along with reductions in self-reported craving and enhancement of EEG correlates of regulation at the final visit. If our predictions hold, findings will serve as important proof-of-concept data on the effectiveness of TDCS in tandem with reappraisal training as a potential treatment augment for CUD as well as elucidating potential mechanisms by which TDCS works. These data will set the stage for future work in larger samples and longer durations investigating TDCS as a method to augment treatment for CUD.