You've heard it a million times before, but you're going to hear it again: smoking is one of the worst things you can do to your body, plain and simple. So why do so many start smoking even though they know it's bad for them? And how do some manage to quit before it becomes a lifelong addiction? We talked with some teens to get the scoop on this stinky habit.

That's Not What Friends Are For!

We'll spare you the afterschool special speeches, but it's a fact — peer pressure is responsible for creating lots of new smokers. A lot of teens who smoke say that they picked up smoking while trying to fit in with older people they know who also puff. Olivia, an 18-year-old living in Los Angeles, says she started smoking when she spent a summer in Ireland. "I had an older group of friends," she says. "They never said, 'You should smoke, that would be cool.' It was just expected."

Other teens start smoking when they're romantically involved with older people who smoke. Kim, a 17-year-old from San Francisco says, "I started smoking the summer before freshman year because I had a girlfriend that was older and she smoked."

Olivia thinks that this phenomenon creates a cycle that gets more and more teens smoking. When she came back from Ireland, where she had started to smoke, she brought the habit back to some of her American friends. "I went from being the victim to being the bad influence," she admits.

Kick It!

Cigarettes are extremely addictive. Most people who smoke really want to quit — so why even consider starting?

While there are still lots of teens who continue to smoke, plenty of them are quitting all the time. A lot of them say they find something else to keep them busy, like playing sports and staying active.

"Sports, I think, is one of the best things to combat smoking cigarettes," says Mike, 17, of Palo Alto, CA. "I didn't smoke any cigarettes for four-and-a-half months last year because of soccer." Cigarettes and sports just don't go together, because smoking reduces lung capacity and affects breathing. Athletes need to be in tip-top shape, and smoking sabotages their game by leaving them huffing and puffing on the field or the court.

Sixteen-year-old San Francisco native Amelia says she quit smoking a week ago because it was interfering with one of her passions: horseback riding. "I started smoking a lot when I broke my collarbone and I couldn't ride," she says. "Smoking affected my riding really badly."

Quitting Does a Body Good

Some other kids are quitting for very serious health reasons. Mike says, "I'm cutting back because I don't want to die of cancer. I want to be able to have a family. I don't want my kids to have me die when they're eight. I think it would be a helluva painful way to go."

Mike is right to be concerned about the health effects of smoking. Recent studies show that half of all teenagers who smoke will eventually die from that bad habit if they don't quit. Besides the millions that die from lung cancer, millions more die from other respiratory diseases and heart conditions caused by smoking.

As if that's not enough reason to quit, a study by Canadian scientists showed that smoking cigarettes (or other forms of tobacco) could be even worse for young women than we already knew. The scientists discovered that teenage girls who smoke could be irreversibly increasing their chances of getting breast cancer — even if they quit smoking in their early 20s. Older studies have shown that smoking is also associated with the development of cervical cancer. Scary stuff!

Family Matters

Rachel, 16, from San Mateo, CA, has some painful family history related to tobacco. Her grandmother, who raised her until she was five, passed away in May due to a smoking-related illness. While she was sick, her grandmother asked Rachel to try to quit. And it worked. "When she died I started smoking less and less. I don't want to end up like my grandmother. She was in so much pain." Rachel is now celebrating five tobacco-free months since she quit.

Enough Is Enough!

While a lot of teens haven't made it happen yet, most of them want to get that dangerous addiction out of their lives. Olivia has gotten over the coolness of cigarettes. "Now I'd say it's just plain addiction," she admits. "I would love to be able to quit."

Amelia, meanwhile, is ready to make a new start. "I'm going to a new school starting on Friday. I start with a clean slate, so why not just stop smoking now." It may take a lot of determination to stop smoking, but you can do it — about 1,000 people quit every day. Let's keep that number growing!