An accumulation of evidence suggests that smoking may be reinforcing, in part, due to nicotine's capacity to enhance attentional processing. Correspondingly, the stimulus-filter model of nicotine reinforcement asserts that nicotine facilitates cognitive performance by acting as a stimulus-barrier, thereby screening irrelevant and annoying stimuli from the smoker's awareness. A review of the available data suggests that while nicotine does appear to reliably enhance sustained, divided, and focused attention, the stimulus-filter model falls short of adequately explaining the findings. An alternative, attention, allocation model of nicotine reinforcement is reviewed, the tenets of which suggest that nicotine differentially augments attentional processing via its propensity to: (a) induce attentional narrowing, and (b) increase perceptual processing capacity. The motivational implications of the model, including smokers' use of nicotine to dampen stress, are discussed.