Men get a bigger kick from coffee than women, says a new research, which found that both sexes get a jolt from the drink.
The study, however, found that while decaf coffee perks up both of the sexes, it affects women more.
In a study on 668 healthy volunteers, an espresso pepped up men after just 10 minutes. Women also became more alert after the beverage, but less so.
The University of Barcelona researchers say some of this effect might be psychological because decaffeinated coffee also worked to some extent.
Progress in Neuro-Psychopharmacology and Biological Psychiatry reports the work.
To reach the conclusion, the researchers asked volunteers to drink either a classic espresso containing 100mg of caffeine or a decaffeinated espresso containing 5mg of caffeine, reports the BBC.
Then, the boffins looked for changes in alertness over the following minutes and hours.
After drinking the classic espresso, both men and women saw an improvement in their activity levels and these effects began after as little as 10 minutes, the study found.
According to the investigators, 45 minutes is the time needed for maximum caffeine concentration to be reached in the blood, but levels reach half this concentration after just a few minutes.
And the effect appeared to be greater in the men.
The decaf coffee had a similar, but weaker effect and tended to be more potent in the women rather than in the men.
Lead researcher Ana Adan said: "Numerous studies have demonstrated the stimulant effects of caffeine, but none of these have looked at their effects in terms of the consumer's gender."