One in 25 youths who surf the Internet are asked at some point during the year to transmit a sexual picture of themselves, a study released Friday finds.

Kids who comply could become both victims and perpetrators of child pornography, says study co-author Kimberly Mitchell, a psychology professor at the University of New Hampshire's Crimes Against Children Research Center.

"They're being asked to produce child pornography," Mitchell says, noting that doing so is a felony. "We think most children don't fully understand the stakes here. They may just see it as rudeness or sometimes even flattery."

The research is based on a nationally representative survey, taken in 2005, of 1,500 youths aged 10 to 17. Nearly 10 percent, or 136, were asked to send photos of themselves; 65 were asked for sexual pictures.

The good news: Only one sent sexual images.

"Kids are not naive about this," says David Finkelhor, the New Hampshire center's director. "On the other hand, given the large number who are solicited and use the Internet, bad things can happen."

Finkelhor says the spread of digital cameras and webcams is putting more kids at risk. He says they may feel less inhibited taking their clothes off in front of a camera than in front of a person.

More kids are posting personal photos online and becoming victims of child porn, says Ernie Allen, president of the National Center for Missing and Exploited Children. He says of the 1,100 kids his center has identified as victims of child pornography, 5 percent produced the photos themselves.

He says kids have to understand that when they post something, they are "potentially sending it to the entire world and can't get it back." He says 89 percent of the 500,000 tips about child exploitation that his center (www.cybertipline.com) has received in the past nine years involve child pornography.

The study also revealed that a rising share of youths were harassed and bullied online, often by peers, and more were exposed to unwanted child porn. One in three youths saw such porn while surfing the Internet in 2005, up from one in four in 2000.

"We're getting a lot of cases" of kids being asked for pictures online, and some use cell phone cameras to comply, says Flint Waters, lead agent of Wyoming's Internet Crimes Against Children task force.

Waters says he hasn't yet prosecuted any youths for producing such photos. "You typically think of the child as a victim," he says. Besides, he adds, "there is no shortage of 40-year-old traffickers to go after."

A well-publicized case of a youth solicited online for sexual photos is Justin Berry, who began posting them at age 13. He testified before Congress last year, when he was 19, and has since helped authorities track the men who enticed him. Berry has not been prosecuted.

Mitchell says those most likely to be asked for pictures were girls, black youths, those with a close online relationship and victims of previous physical and sexual abuse. She says only 12 percent of the 65 instances in her study involving requests for sexual pictures were reported to authorities.