Attentional bias modification (ABM) to avoid smoking-related cues is a potentially new intervention in addition to existing therapy to stop smoking. We examined immediate and long-term changes in attentional bias and treatment outcomes from multiple ABM sessions in 67 smokers trying to quit. After assessing attentional bias baseline, participants were randomly allocated to one of three training groups: three sessions of ABM (avoid 3); two sessions of placebo-ABM and one session of ABM (avoid 1); and three sessions of placebo-ABM (avoid 0). At baseline, all groups had similar positive attentional bias, which became negative at 24h post-training. After 1 month, avoid 1 and avoid 3 still exhibited negative attentional biases. Only avoid 3 maintained this effect at 6-month, but not at 12-month assessments. ABM produced a long-lasting automatic and maintained avoidance to smoking-related cues which depended on number of sessions; however its effects on treatment outcomes are uncertain.