They spend at least two hours a day online, usually playing games or chatting. Of those, up to a quarter million probably show signs of actual addiction, like an inability to stop themselves from using computers, rising levels of tolerance that drive them to seek ever longer sessions online, and withdrawal symptoms like anger and craving when prevented from logging on.

To address the problem, the government has built a network of 140 Internet-addiction counseling centers, in addition to treatment programs at almost 100 hospitals and, most recently, the Internet Rescue camp, which started this summer. Researchers have developed a checklist for diagnosing the addiction and determining its severity, the K-Scale. (The K is for Korea.)

In September, South Korea held the first international symposium on Internet addiction.

“Korea has been most aggressive in embracing the Internet,” said Koh Young-sam, head of the government-run Internet Addiction Counseling Center. “Now we have to lead in dealing with its consequences.”

Though some health experts here and abroad question whether overuse of the Internet or computers in general is an addiction in the strict medical sense, many agree that obsessive computer use has become a growing problem in many countries.

Doctors in China and Taiwan have begun reporting similar disorders in their youth. In the United States, Dr. Jerald J. Block, a psychiatrist at Oregon Health and Science University, estimates that up to nine million Americans may be at risk for the disorder, which he calls pathological computer use. Only a handful of clinics in the United States specialize in treating it, he said.

“Korea is on the leading edge,” Dr. Block said. “They are ahead in defining and researching the problem, and recognize as a society that they have a major issue.”

Image Campers are under constant surveillance, even while they sleep. Credit... Seokyong Lee for The New York Times

The rescue camp, in a forested area about an hour south of Seoul, was created to treat the most severe cases. This year, the camp held its first two 12-day sessions, with 16 to 18 male participants each time. (South Korean researchers say an overwhelming majority of compulsive computer users are male.)