How essential are cigarettes in movies?

James Dean, Audrey Hepburn and Roger Moore - to name just a few film celebrities - all smoked like fiends on the screen.

For years, the World Health Organization (WHO) has been fighting against tobacco consumption, including smoking in movies.

Films showing use of tobacco products have "enticed millions of young people to start smoking," says the new WHO initiative "Smoke-free movies: from evidence to action" - the third edition since its launch in 2009.

"With ever tighter restrictions on tobacco advertising, film remains one of the last channels exposing millions of adolescents to smoking imagery without restrictions," according to Douglas Bettcher, WHO's Director for the Department of Prevention of Noncommunicable Diseases.

Getting the young hooked

"Smoking in films can be a strong form of promotion for tobacco products," Bettcher says, adding that the 180 parties to the WHO Framework Convention on Tobacco Control (WHO FCTC) are "obliged by international law to ban tobacco advertising, promotion and sponsorship."

In 2014, smoking was found in 44 percent of all Hollywood films, and 36 percent f films rated for young people, the WHO says. Studies in the US have shown that on-screen smoking accounts for 37 percent of all new adolescent smokers.

The prevalence of on-screen cigarettes has helped create film characters that would be unthinkable without them. Click through the gallery above for a look at 10 smokey films.