The effects of cigarette smoking on the electroencephalogram (EEG) of smokers were examined in a study involving both task and no-task conditions. Non-smoking subjects were employed as controls. In light inhaling smokers, (depth of inhalation inferred from pre- to post-smoking changes in tidal breath carbon monoxide), smoking was found to attenuate EEG activity in the delta, theta, and alpha frequency bands, as well as facilitate behavioral performance. For theta, the attenuation was lateralized over the right frontal cerebral hemisphere. In deep inhaling smokers, smoking produced a symmetrical central midline increase in beta2 magnitude, an EEG effect that in the benzodiazepine literature is associated with anxiety relief.