NEW YORK — A recent report that MySpace removed 90,000 sex offenders from its Web site had me wondering: Maybe all those moms who spy on their kids online are doing the right thing.

Yeah, that's right. Moms are spying. They're reading kids' text messages, hacking into their e-mail and checking what Web sites they've been visiting.

Now, I admit to having been a Mommy Mata Hari at one time. I used to check my son's MySpace page to see what he was up to. I even joined Facebook in order to "friend" him.

I didn't realize he'd have to approve me before I could access his Facebook profile. He refused.

So I resorted instead to that time-honored maternal tradition: Nagging.

"Don't friend strangers! Don't say stupid things online! Don't put up pictures of yourself on a Web site that will cause your future wife to divorce you!" (Not to mention that could cause your current mother to have a heart attack.)

But is a talking-to from Mom enough to protect teens online?

I sought opinions from Dr. Herbert Mandell, a psychiatrist and medical director of Kids-Peace, a 126-year-old national children's crisis organization, and also from North Carolina's attorney general, Roy Cooper, who co-chairs the State Attorney General Task Force on Social Networking. The task force worked with MySpace to find and block those sex offenders.

To my surprise, the lawman from North Carolina and the psychiatrist from KidsPeace both agreed that it's more effective for parents to talk to teenagers than to spy on them.

"Talk with your kids about Internet use, just like you would talk to them about drinking, drugs, sex or anything else," Cooper said. "The Internet is an incredible tool. Your children can find answers with the click of a mouse that used to take hours at the card catalog. But it has a dark side, particularly when children communicate online with people they don't know."

Cooper pointed out there are risks not only on Facebook and MySpace, but also with Xbox Live, where kids compete against players they may not know.

He added that "parents should talk to kids about things they post online about themselves," including pictures, videos and comments that can be seen by strangers, future employers and others. "And tell them not to accept friends on social networking sites unless they know who they are."

Mandell said studies show that parents who talk to their kids — about the Internet or anything else — have more of an impact than you might think.

"They may appear to not be listening, but they are," he said. "People who have studied child and adolescent behavior have seen lots of evidence over a span of decades that not only do children listen to their parents, but most of the time they are listening pretty closely. They know exactly what your standards are, and if you have a healthy relationship, they incorporate those standards and internalize the values being taught."

Both Cooper and Mandell added a few caveats. Mandell said parents are justified in investigating what teens are up to if there is evidence of substance abuse or other signs of trouble — inappropriate relationships, a plunge in grades, or a psychiatric or developmental disorder.

Cooper added to the list of warning signs unsolicited gifts from strangers and mysterious long-distance phone calls.

Cooper also said parents should supervise younger children more closely than teens, including setting password-protected parental controls that allow you to block objectionable content, and letting them know you'll be checking the Internet history to see what Web sites they're visiting. He did that when his two children were younger.

But does Cooper spy now that his kids are teenagers?

"I don't," he said, adding that he thinks his teens are mature enough to understand the risks and make the right decisions.

That's a philosophy Mandell approves of. "There's no reason to track every movement your kids are making unless you haven't built up the sense of trust and healthy flow between parent and child that takes years to achieve," he said.

Mandell said digital spying not only undermines trust, but kids can outsmart us by deleting incriminating messages, making calls from friends' phones and disabling software.

"Of course they can beat you at that game," he said. "They're more technologically savvy than we are."

As for me, my son still won't friend me on Facebook.

But that's OK. I found lots of mom friends on the site. They'd all been rejected by their kids, too.

Beth J. Harpaz is author of several books, including "13 Is the New 18."