Quick. Think back to the Moscow summit. It was only a few weeks ago.

What did it produce?

An end to the nuclear arms race? A Middle East agreement? Superpower cooperation to end the Iran-Iraq war?

None of the above.

President Reagan, who now leads all U.S. chief executives in superpower summits with four of them, gave his enthusiastic support to Mikhail Gorbachev's campaign to restructure the Soviet economy. That was significant, and very dramatic, but it was about all that happened. Here was the American president, a pronounced critic of communism, in Moscow endorsing Gorbachev's perestroika program _ and blaming the bureaucracy, not the Kremlin, for violations of human rights.

But the agreements reached in Moscow were on the level of fishing and maritime pacts _ not the sort of accords that require the immense political power of the U.S. president and the Soviet general secretary.

Charles M. Fairbanks Jr., a scholar at the Johns Hopkins School of Advanced International Studies, has concluded that summits frequently fail to make effective use of the considerable authority of national leaders.

In a recent study, and an interview, Fairbanks said summits frequently become occasions of drama rather than instruments of coordinated diplomacy.

The Moscow summit, he said, "produced essentially nothing in diplomatic terms. The most important thing, I think, that took place was Reagan speaking to a Soviet audience. That probably served a useful function. But it's certainly not the function a summit is held out to serve." Summits have come to be understood as occasions for personal negotiations between immensely powerful political leaders. At Reykjavik, in 1986, for instance, Gorbachev presented Reagan with a series of historic arms control proposals.

These included the abolition of ballistic missiles and, possibly, all nuclear weapons.

Normally, diplomats at lower levels work for years to reach the point where such cosmic decisions can be made at the summit.

"The advantages of traditional diplomacy are that it is calm, quiet and usually secret," Fairbanks writes. "Summit conferences, however, are very dramatic."

Gorbachev used the Reykjavik summit to symbolize his dedication to arms control. It also produced pressure for concessions from Reagan, but they were later withdrawn. The idea of banning ballistic missiles was quickly and quietly buried only a few months later.

In the end, Reykjavik did not produce anything substantial.

Because summits are so dramatic, they create a desperate need for success. And this, Fairbanks said, gives birth to a tremendous temptation to proclaim fictitious results.

Reporters get sucked in. Trivia is exalted. But sometimes all that really happened is that the two most powerful leaders in the world met.

Time magazine seemed to realize this in its account of the 1967 summit meeting between President Lyndon Johnson and Soviet Premier Alexei Kosygin in Glasboro, N.J., in 1967.

"In the aftermath of history's first hot-line diplomacy," Time reported, "the most significant aspect of the Smalltown summit was that it happened."

Then there are the summits which really produce results.

President Jimmy Carter invited Prime Minister Menachem Begin of Israel and President Anwar Sadat of Egypt to Camp David in 1978 and overcame differences between the two Middle East leaders since their own summit meeting a year earlier.

The result was the 1979 peace treaty between Egypt and Israel.

Reaching back into history, Fairbanks recalls the long-forgotten summit held between Wilhelm II of Germany and Nikolai II of Russia at B'yorkyo in July 1905.

In terms of immediate results, he writes, "this was perhaps the most successful summit in history."

Germany signed an alliance with Russia that might have changed the course of history.

But even that treaty was quickly canceled.

Nikolai's foreign minister explained to the czar that it undercut Russia's longstanding alliance with France and had to be discarded.

Nine years later, Russia went to war with Germany as an ally of France. The war devastated Russia and paved the way for the Bolshevik revolution.