"We found that if you get kids to answer just two simple questions - 'would it be easy for you to get a cigarette?' and 'do you have friends who smoke?' - you can identify those who are at high risk of becoming regular smokers," said lead author, Chyke Doubeni, PhD, with the University of Massachusetts Medical School.
"Saying yes to either should raise a red flag and prompt doctors and others to talk with parents and kids about how to avoid smoking," Doubeni added.
For the study, researchers interviewed 1,195 sixth-graders in Massachusetts who had never before puffed on a cigarette or who smoked less than once a week.
They followed them from January 2002 to February 2006.
Over the four years of the study, 177 students tried out smoking and 109 became regular smokers.
The study showed that all those who picked up the habit either agreed with the statement 'it would be easy for me to get a cigarette' or acknowledged having a friend who smoked - or both.
The researchers also found that perceptions of accessibility and prevalence of peer smokers both intensified, as the kids got older.
At the beginning of the study, 21 percent of the participating students perceived cigarettes as easily accessible and only 9 percent had friends that smoked.
By the fourth year of the study period, 50 percent perceived easy access to cigarettes and 32 percent had friends who smoked.
Also, researhcers found that as they get older, kids appear to become more aware of which stores sell cigarettes.
"The take home message is clear: knowing that it is easy to get cigarettes is like adding fuel to the fire when it comes to youth smoking," Doubeni said.
"And having a friend who smokes naturally makes cigarettes seem readily available. Ultimately, the kids who reported both peer smokers and easy access were the ones most likely to become regular smokers, compared to those who were exposed to none of those factors," Doubeni added.
The study is published in the current issue of Annals of Family Medicine.