WARNING: movies can seriously make you want a cigarette. After years of decline, smoking scenes in Hollywood films, especially those rated for young, impressionable audiences, are back in style.

Those who thought that the Hollywood glamorisation of tobacco was over when James Bond gave up his 60-a-day habit should think again. According to researchers at the University of California at San Francisco, 80 per cent of films rated PG-13 contain smoking scene. Recent offenders include Anchorman, set in a 1970s television studio, and Ocean’s Twelve, a comedy about a group of glamorous thieves.

Jude Law, the British actor, was singled out over his nicotine addiction in films including Closer, Alfie and The Aviator. Uma Thurman played a seductive smoker in Pulp Fiction. Even Julia Roberts, a sweet-natured romantic lead, was criticised for lighting up, as was Brad Pitt.

Another remarkable fact uncovered by the researchers was that the number of yellow- fingered scenes in all American films is back to levels not seen since the 1950s. As with almost all things Hollywood, the number of people who smoke on the silver screen bears no relation to real life.

The number of American smokers has halved since the 1950s. In the movies, the amount of tobacco use has gone up from 10.7 “smoking events per hour” in 1950 to 10.9 in 2002. Everything from a character lighting up to a shot of a tobacco advert counts as a smoking event. According to the study, conducted by Stanton Glantz and Annemarie Charlesworth, and published in the December issue of Pediatrics, on-screen smoking causes 390,000 teenagers a year to try their first cigarette. That is half of all new teenage smokers.

“We now have multiple studies making the same point: adolescents who see a lot of smoking in the movies are more likely to start smoking themselves,” said Mr Glantz, who reviewed more than a decade’s worth of data for his report. Health researchers have long urged an R-rating for films that depict smoking.

A website and blog, which can be found at www.scenesmoking.org, keeps track of smoking scenes in all new films. Those with no smoking, such as Harry Potter and the Goblet of Fire (PG-13), are marked with a symbol of healthy pink lungs. Those such as Rent (PG-13) earn a pair of cancerous black lungs. The remark posted next to Rent says: “I’m not sure how some of the characters will do, health-wise, if they keep smoking.”

The website urges smoking scenes to be deleted even when they are factual. Walk the Line (PG-13), the biopic of Johnny Cash’s boozy, drug-addled life, merits the following comment: “This movie receives the automatic black lung for tobacco use around a child and pregnant woman.”

Mr Glantz and Ms Charlesworth are a little easier on films such as Good Night, and Good Luck, about the smoky 1950s television newsroom of Edward R. Murrow. “The cigarette was a defining part of the persona of Edward Murrow, who ended up dying of lung cancer.”

The Motion Picture Association of America disputes the findings, quoting industry statistics that show that only about half of PG-13 rated films over the past two years include smoking scenes. “Everybody agrees that smoking is a serious health problem and that our industry shouldn't be encouraging or glamorising smoking,” a spokeswoman said.

Yet the research also found that, whereas real-life smokers are often poor, tobacco users in the movies are wealthy. Sometimes, in the case of the extraterrestrial comedies Men in Black and Men in Black II, they are not even human.