"Study after study has shown that... on-screen smoking has a powerful influence on behavior, " Fiore says.

CNN: Should smoking trigger an R rating?

Kids under the age of 18 are particularly vulnerable to images of high-wattage stars smoking cigarettes on the big screen, partly because adolescents, similar to very young children, are prone to mimic behaviors they see others trying, Sargent says.

CNN: Should smoking trigger an R rating?

PG-13 films account for nearly two-thirds of the smoking scenes adolescents see on the big screen, according to the two-year study, which surveyed roughly 5, 000 children ages 10 to 14 about the movies they'd seen and whether they'd ever tried a cigarette.

CNN: Should smoking trigger an R rating?

The study, which appears in the August issue of the journal Pediatrics, was designed in part to refute the notion that it's difficult to untangle movie smoking from the many other situations, both on-screen and off, that may contribute to adolescent impulses.

CNN: Should smoking trigger an R rating?

While the study can't prove that one is related to the other, the findings would seem to support what critics have long said: Smoking by glamorous (or even not-so-glamorous) people on the silver screen is like free advertising for cigarettes.

CNN: As movies portray fewer smokers, fewer teens light up