Regular cigarette smokers (n = 15), overnight deprived smokers (n = 15) and nonsmokers (n = 20), were assessed on a battery of mood questionnaires and cognitive performance tasks, before and after a cigarette/rest period. At the initial session, deprived smokers reported significantly greater feelings of stress, irritability, depression, poor concentration and low pleasure, than both nondeprived smokers and nonsmokers tall comparisons, p < 0.01). After the rest/cigarette break, the mood states of all three groups became generally similar, although the previously deprived smokers still reported elevated depression. These findings suggest that mood gains after smoking reflect the simple reversal of abstinence effects. On the cognitive tasks, there were no significant differences in letter cancellation performance between subgroups, either before or after smoking. With mental arithmetic, abstinent and nonabstinent smokers attempted more problems than nonsmokers, both before and after the rest/cigarette break. This is suggestive of faster cognitive processing in smokers, irrespective of their nicotine status. However, the cognitive performance data were untypical in various ways and need replication. (C) 1998 John Wiley & Sons, Ltd.