Etan Patz, whose disappearance here in 1979 started a national campaign to publicize the problem of missing children, may be alive in Israel, federal law enforcement officials said today.

U.S. Attorney Rudolph W. Giuliani met with Israeli journalists here this week and asked them to publish photographs of the youth when he was 6 and a composite computer photograph of how he might look now.

"There is no hard evidence, but there is a reasonable assumption that Etan Patz might have been in Israel," said Giuliani, who reopened the case six months ago.

The Israeli investigation became public this week when a Romanian-born woman in Queens noticed Patz's photograph in the current issue of a Romanian-language magazine from Israel and telephoned the New York Post. The caption identified the youth as "Etan Ben-Haim," which means "Etan Son-of-Life."

Federal officials said the photograph was published in the magazine, Revista Mea, at the request of Assistant U.S. Attorney Stuart GraBois and FBI agent Kenneth Ruffo, who traveled to Israel last month to follow up several leads.

The magazine had received Etan's picture anonymously in 1981, one of a series circulated across the United States on posters and in newspapers after his kidnaping, and published it then without explanation, apparently as a filler. The picture, labeled Etan Ben-Haim, had been received in an envelope postmarked Kiryat Bialik, a working-class suburb of Haifa.

In publishing the picture again this month, Revista Mea flanked it by pictures of two other small boys. The accompanying three-paragraph story said the pictures had appeared previously in the magazine and noted that the boys would now be 13 and ready for their bar mitzvahs. The story requested new photographs and information, ostensibly for a follow-up article.

The photograph's initial appearance in Revista Mea led to a theory among U.S. investigators that Etan might have been kidnaped by Romanian Orthodox Jews. A law enforcement source said today that the lead had been investigated by Israeli police and that, in reviewing the files recently, "we just became aware that there had been gaps in the coverage of that lead and we decided to go over it once more."

Patz's father, Stanley, told the New York Post, "I don't expect anything to come of it. Let's see what happens."

A federal source confirmed that an inquiry is also under way into whether Patz was kidnaped by members of the North American Man Boy Association, a group that promotes sexual relations between men and boys. However, one FBI source cautioned that "the trail is pretty cold" on all the leads.