Forget the convertible. A boob job is the latest must-have on your teen daughter's graduation list.

The number of 18-year-olds who underwent breast-implant surgery nearly tripled last year — from 3,872 in 2002 to 11,326 in 2003, according to the American Society for Aesthetic Plastic Surgery (search).

"There is a trend in which parents are giving implants as a gift, including as a graduation present," said Dr. Stephen Greenberg, who practices in Woodbury, L.I., and Manhattan.

Popular, well-endowed teen idols, like Britney Spears (search) and Lindsay Lohan (search), as well as reality-TV shows like "Extreme Makeover" and "The Swan," have made some girls dislike their own bodies, experts said.

"The media and fashion industries emphasize breasts and a curvaceous figure," said Dr. Leroy Young, co-chair of the American Society for Aesthetic Plastic Surgery's breast-surgery committee. "There's no advertising [for implants] targeting that age group, but the images are all around them."

Docs say most young women seek the enhancements out of frustration with the way clothing or bathing suits fit.

"It's usually an internal issue — they want to feel more feminine, less self-conscious," said Young.

"Most do it as a self-esteem booster," Greenberg echoed.

Last week, the FDA released its new consumer handbook on implants — and included graphic photos of possible side effects.

Kathy Keithley Johnston, executive director of Toxic Discovery (search), an anti-implant group in Columbia, Mo., praised the FDA booklet, noting, "a picture is worth a thousand words."

That parents willingly shell out $3,500 to $7,000 for a daughter's implant surgery infuriates Johnston, a registered nurse who claims her implants made her seriously ill.

"They say it's the girls making the decisions — but it's the parents writing the checks. How is that any different than buying them alcohol or cigarettes. Shame on any parent that would endanger a teenager that way."

The increasing popularity sparked Greenberg to set up a special program for young women considering implants.

"You really need to make sure they're physically ready — that they've stopped growing — and psychologically mature," he said. "In consultations, I try to get a solid idea of what their mindset is and how realistic they are about the outcome. They also need to understand this is real surgery."

The blossoming teen trend worries Johnston, who travels the country explaining the hazards of implant surgery to high school and college students — an uphill battle, she said. Her presentation includes horrific photos of disfigurement from implant removal.

"If you're a teenager, who are you going to believe? An advocacy group, or a surgeon who's promising to make you look better?" Johnston said.

Among FDA- and doctor-cited risks are surgical bleeding and infection. Implants also deflate or rupture over time; they can result in loss of breast volume, misshapenness or wrinkling; and can affect mammograms, making it tougher to detect breast cancer.

There's also a limited shelf life — breast implants usually have to be replaced at least once, and as many as several times, requiring additional surgery.

The vast majority of plastic surgeons use saline implants, which have been OK'd by the FDA for use on women over 18. In teens younger than 18, the surgery must be for medical reasons. Silicone implants are only available through FDA-approved medical studies.

Plastic surgery, overall, is on the rise, noted Greenberg. With 280,401 breast augmentations in 2003 — a 12 percent spike — "it make sense that the numbers have grown with younger patients, as well," he said.