To demonstrate the positive effects of smoking on spatial-imagery processing, behavioral (hit ratio and reaction time) and physiological indices (EEGs and HR) were examined in 12 student volunteers. Subjects performed two spatial-imagery tasks, one mental rotation and the other mental paper-folding. The two tasks were performed before and after smoking and the results compared. Subjects participated in both control and smoking sessions. Reaction time decreased after smoking, while the hit ratio did not change. EEG contour maps derived from 12-channel records of the beta band showed activation of the frontal area during the spatial-imagery processing. After smoking, EEG laterality showed increased right-hemisphere dominance. These findings implied that smoking facilitated selective activation of the hemisphere and did not support Gilbert and Wesler's hypothesis of left-hemisphere priming. Psychophysiological mechanisms of the effects of smoking were discussed.