The first kidnaping of a child for ransom here this week has sent shock waves through this tiny Persian Gulf nation, whose huge oil wealth makes it potentially fertile ground for such activities.

While the two kidnapers involved were caught within 20 hours after they seized the child of a well-known Kuwaiti businessman, the fact that one was a Kuwaiti has caused a major sensation.

Until recently, Kuwait was relatively crime-free, particularly free of rapes, murders and kidnaping. But the onset of what Kuwaitis like to think of as Western social diseases was highlighted last fall when three persons were hanged for kidnaping, raping and killing two young girls; then two others were hanged for the armed robbery and murder of a money changer. All were foreigners.

Particularly compared with the United States, Kuwait has a low incidence of violent crime. Kuwaitis tend to blame what problems they have on the large foreign community--particularly Asians, Egyptians and Palestinians--that constitutes more than half the country's 1.2 million population and 70 percent of the work force.

But the latest kidnaping was the first time that such a crime involved a Kuwaiti from a well-off family. He was identified as Fahd Abdul Salem Najar, 26, an interior decorator. His accomplice was Egyptian.

The kidnaping took place early Tuesday when the two men seized the sleeping 4-year-old son of the Kuwaiti businessman, Salah al Sultan, from his home and demanded $540,000 for his release.

The police were able to track the child, Samy, by interrupting all public telephone services as well as the thousands of phones installed in cars, thus forcing Najar to use a private phone.

The first call came within hours of the kidnaping from the Hilton Hotel, where Najar had a friend working as a barber who allowed him to use his phone. The friend was apparently unaware of the kidnaping.

The friend later told police he knew Najar had access to a beach home in Kheiran, 80 miles south of the city. The police raided it, seized the kidnapers and freed the child unharmed.

For 20 suspense-filled hours, everyone in the government followed the case minute by minute, according to local press reports, which have treated the kidnaping as the crime of the century.

Perhaps most disturbing to Kuwaitis was why Najar, himself the son of a well-to-do Kuwaiti businessman would be involved in such a crime. The answer seems to be that the enormous wealth of this country--Kuwait has the highest per capita income anywhere in the world--is spawning its own social diseases.

Najar, it seems from press reports and one person who knew him, had failed in his studies and was taking drugs while working in his father's business. The week before the kidnaping, he either left the family or was disowned because of a disagreement with his father.

Penniless and possibly wishing to embarrass his family in retaliation, he turned to kidnaping, which seems to have been an amateurish operation with little hope of success in this small, closely knit society.

Many Kuwaitis are calling for his death to make an object lesson out of him. But most observers expect that Najar will be sentenced to life in prison instead, since he is a Kuwaiti and the child was not harmed.

Brigadier Abdulaziz Jumaa, a security official who briefed the press on the rescue operation, said, "We hear of kidnaping cases in the West but never here. Islamic society abhors this crime, and we are greatly relieved to see such a swift action by our police."