They found that smokers itch for a cigarette when they watch someone light up in a film as the action is embedded in their minds.
Brain areas known to interpret and plan hand movements lit up as the smokers saw the familiar action, as if they too were about to light up, the team from Dartmouth College said. However, this response wasn't recorded in non-smokers.
The results could provide additional insight for people trying to overcome nicotine addiction.
Study co-author Dylan Wagner, said: 'Our findings support prior studies that show smokers who exit a movie that had images of smoking are more likely to crave a cigarette, compared with ones who watched a movie without them.
'More work is needed to show whether brain activity in response to movie smoking predicts relapse for a smoker trying to quit.'
In the study, published in The Journal of Neuroscience, 17 smokers and 17 non-smokers watched the first 30 minutes of the movie 'Matchstick Men' while having an MRI scan of their brains.
The researchers chose the movie because it prominently features smoking scenes but otherwise lacks alcohol use, violence, and sexual content.
The volunteers were unaware that the study was about smoking. When they viewed smoking scenes, smokers showed greater brain activity in a part of the parietal lobe called the intraparietal sulcus, as well as other areas involved in the perception and coordination of actions.
'Smokers trying to quit are frequently advised to avoid other smokers and remove smoking paraphernalia from their homes, but they might not think to avoid a movie with smoking content,' Mr Wagner said.
The Centers for Disease Control and Prevention has warned that exposure to onscreen smoking in movies makes adolescents more likely to smoke.
According to their 2010 report, tobacco use in films has decreased in recent years, but about half of popular movies still contained tobacco imagery in 2009, including half of those rated PG-13.
Dr Scott Huettel of Duke University, an expert in the neuroscience of decision-making who was unaffiliated with the study, said scientists have long known that visual cues often induce drug cravings.
'This finding builds upon the growing body of evidence that addiction may be reinforced not just by drugs themselves, but by images and other experiences associated with those drugs,' he said.