As professor John Decker reviewed bail guidelines and other criminal procedures one recent evening, some students in his DePaul University law class had other things on their minds.

One student shopped on eBay for Cirque du Soleil tickets. Another switched between checking her e-mail and Fox News headlines. And, from the back of the room, a 24-year-old White Sox fan refreshed his screen to see whether the team was still ahead of the Pirates.

"I do it all the time, just looking at the scores," said Viet Pham, a first-year law student. "Sometimes we go off on a tangent, so I do it to keep awake."

With universities rapidly installing wireless networks, Internet surfing has taken the place of the crossword puzzle as the most popular classroom distraction. Some professors are so fed up, however, that they're banning laptops or finding ways to shut off the wireless capabilities in their classrooms.

Bruce Ottley, another DePaul law professor, hasn't taken it that far, but his syllabus contains a stern warning:

"If you do bring a laptop computer to class, it is to be used EXCLUSIVELY for taking notes," the syllabus says. "Students found to be using their laptops in class to surf the Internet, to send or receive e-mails, or for other non-class related purposes will be required to leave and will not be permitted to return for the remainder of the class."

DePaul installed wireless technology several years ago, placing it among the 29 percent of colleges where students, as of last fall, can check their e-mail from anywhere on campus. Just five years ago, only 4 percent of campuses had wireless networks, according to the Campus Computing Project, which studies information technology in higher education.

Told of the Web surfing going on in his class at DePaul that recent night, Decker said that he doesn't plan to limit laptop use or block Internet access.

"They are adults and in some respects, I feel like if they are not there, or not paying attention to what is going on and shopping for shoes or whatever the case may be, it's their loss," he said.

Chris Niro, one of the few laptop-free students that night, said he self-censored earlier this year, realizing he wasn't concentrating on lectures.

"It was far too distracting," said Niro, 26, a second-year DePaul law student. "It was easy when you got bored to check your e-mail or the score of the basketball game."

At the University of Michigan law school, students don't have that choice — a computer system blocks them from being able to access the Internet during their scheduled class times. Some students have learned how to get around the system by borrowing the account names and passwords of students who aren't in class at the same time.

"One of my jokes is that I'm willing to compete with Minesweeper, but not with the entire Internet," said Michigan law professor Don Herzog, who initiated the faculty discussion that led to the Internet ban.

Herzog said that when he first suspected students were checking the Internet during class, he sat in the back of his colleagues' classes as an experiment and saw that about 85 to 90 percent of students were doing so. Even a special lecture by a popular faculty member didn't stop students from getting distracted.

"One was shopping at EddieBauer.com, another student was looking for an apartment in San Francisco and (instant messaging) a friend of his about neighborhoods," he said.

Faculty members said the issue tends to affect graduate and professional school students more than undergraduates, who are less likely to bring their laptops to class. The problem, professors say, is that Internet use can be distracting not just for the user, but also for anyone sitting behind that student. And in a law school class, where students are called on to answer questions, a preoccupied student can slow the discussion.

That's among the reasons why Harvard University law professor Bruce Hay banned the computers from his wireless-enabled lecture hall this past year.

"Frankly, if I was in their position, I would be tempted to check my e-mail. I understand it," said Hay, who teaches civil procedure and law and psychology. "But when a lot of people do it, it becomes demoralizing and distracting."

Hay, who once spotted a student watching a DVD on his laptop, said students have accepted the ban. Four or five other Harvard faculty members also prohibit them, and he expects more to join them.

"My sense is that the quality of classroom discussion has gone down in the past five or six years. I think that more or less corresponds with the widespread introduction of laptops," he said.

At the University of Chicago law school, professor Randy Picker has no intention of banning laptops or Internet access. About 90 percent of his students bring computers to class, and he encourages them to use the university's wireless connection to pull up his PowerPoint slides or research a topic raised during class discussion.

"Obviously the Web is something of a distraction, but there are a lot of distractions," Picker said. "My job is to make them want to pay more attention to me than what is on the screen."