Cigarette smoking is still quite prevalent despite public education campaigns, and more understanding about the processes that relate to relapse and abstinence is still needed. In the current study, recent abstinent smokers who were later deemed to be relapsers or abstainers responded to the color of smoking-related and neutral words in a Smoking Stroop Task while high-density EEG was recorded. One-month Abstinent smokers responded more slowly to smoking words relative to control participants who had never smoked, while Relapsers did not show this effect. One-month relapsers displayed greater voltage of the late positive potential (400-600 ms, aLPP) over the left frontal scalp relative to both one-month abstinent smokers and never smokers. Our findings suggest that smoking cues are more salient for abstinent smokers who are prone to relapse, and this ERP activity evoked by cigarette cues may be a potential biomarker for relapse susceptibility. In contrast, successful abstainers may respond to smoking cues by engaging top-down cognitive control mechanisms leading to less aLPP voltage but greater RT interference. This appears to be the first ERP study to use a Smoking Stroop Task and a high-density electrode array to characterize the spatiotemporal dynamics of smoking-related cue reactivity in abstinent smokers who successfully abstained for one month and those who later relapsed within the same period.