A burgeoning literature suggests that attentional factors are associated with smoking behavior (e.g. direct nicotine effects and smoking withdrawal). This study examined differences in attentional processing between nonsmokers, satiated smokers and overnight nicotine-deprived smokers by comparing the amplitude of the P300 (P3) component of the event-related brain potential (ERP) elicited during a go–nogo task. We also examined the moderating effects of a common dopamine receptor genotype and state negative affect (SNA) on this ERP index of attention. Nonsmokers relative to smokers had greater nogo P3 amplitude. Carrying the A1 allele at the dopamine receptor D2 (DRD2) Taq1A polymorphism site moderated the effects of withdrawal on nogo P3 amplitude, suggesting the A1 allele is a vulnerability marker for withdrawal-related attentional deficits. Increased SNA also predicted attenuated P3 amplitude among deprived smokers. These findings suggest that DRD2 status and SNA moderate the effects of smoking status and withdrawal on neurocognitive variation during attentional processing. This research contributes to a better understanding of the role of individual differences and attentional processing in smoking behavior.