Passing a flirtatious note to get someone's attention is so yesterday. These days, young people use technology instead.

About a third of young adults 20-26 and 20 percent of teens say they've sent or posted naked or semi-naked photos or videos of themselves, mostly to be "fun or flirtatious," finds a new survey.

A third of teen boys and 40 percent of young men say they've seen nude or semi-nude images sent to someone else; about a quarter of teen girls and young adult women have. And 39 percent of teens and 59 percent of those 20-26 say they've sent suggestive text messages.

"One of the reasons we wanted to do the survey was to put some sort of structure around the anecdotes," says Marisa Nightingale of the nonprofit National Campaign to Prevent Teen and Unplanned Pregnancy, which commissioned the survey with the Hearst Digital Media site CosmoGirl.com. Chicago-based market research firm Teenage Research Unlimited surveyed 1,280 teens and young adults online between Sept. 25 and Oct. 3.

About 80 percent of teens 13-17 and 93 percent of those 18-24 use cell phones, estimates Nielsen Mobile; most cells now have built-in cameras. Though photos are often intended for a boyfriend or girlfriend, they are increasingly shared, especially after a breakup.

High school senior Mayron Gezaw, 17, of Fairfax, Va., says a nude photo that she heard a girl sent her boyfriend showed up on her phone last year. "The whole class was sharing it by the end of the day. ... The guys said, 'She's so hot.' The girls were more like, 'I feel sorry for the girl,' or they just lost all respect" for her.

Most of those surveyed (73 percent) said they knew sending sexually suggestive content "can have serious negative consequences," yet 22 percent said it's "no big deal."

Still, news reports increasingly document school-related or legal repercussions after indecent photos pop up online. And lawyers say there are many unanswered questions about whether young people who send their own photos could face prosecution for obscenity or child pornography.

"I do think people over 40 grew up with a different sense of this stuff," Nightingale says. "Unfamiliarity with the technology plus hearing about some of these extreme stories on the news can combine to make parents feel so overwhelmed and intimidated that they just don't want to deal with it."

The survey also found 48 percent of teens and 64 percent of young adults have received sexually suggestive text messages; 22 percent of teens and 28 percent of young adults say they are "more forward" digitally than "in real life."

Matthew Younger, 17, of Takoma Park, Md., says he has seen the pictures on other people's phones.

"I feel pretty sure if you ask any high school boy across America, they'll say yes, they've seen this kind of thing. It's incredibly widespread."