Objective Finding new tools for conventional management of alcohol disorders is a challenge for psychiatrists. Brain indications related to cognitive functioning could represent such an add-on tool. Methods Forty alcohol-dependent inpatients undertook two cognitive event-related potential (ERP) tasks at the beginning and at the end of a 4-week detoxification program. These comprised a visual oddball task investigating cue reactivity and a Go/No-go task tagging inhibition using oddball P3d and No-go P3d ERP components. Three months after discharge, the patient group (N = 40) was split into two subgroups: patients who remained abstinent during this post-treatment period (90 days; n = 15), and patients who relapsed (mean time: 28.5 ± 26.2 days; n = 25). Pattern changes of both ERP markers (oddball P3d and No-go P3d) during the detoxification were compared to differentiate these populations. Results Abstinent patients exhibited similar P3d responses devoted to alcohol cues in Sessions 1 and 2, but an increased No-go P3d devoted to No-go trials in alcohol-related contexts in Session 2 compared to Session 1. Conclusions Specific cue-reactivity and inhibitory neurophysiological markers subtend a further three-months of complete abstinence. Significance Monitoring these ERP changes during detoxification may provide important clues regarding patients’ future abstinence vs. relapse.