THE SESSIONS BETWEEN President Reagan and Mikhail Gorbachev on the shores of Lake Geneva this week -- the first meeting of U.S. and Soviet leaders since 1979 -- marks a significant break in the history of superpower summits.

Reagan is taking a different tack than his recent predecessors. Presidents Richard M. Nixon, Gerald R. Ford and Jimmy Carter used summits to negotiate specific arms-control agreements, resulting in the SALT I and SALT II accords of the 1970s. Reagan says he does not want to dicker in Geneva in this way but seeks to "eliminate the distrust" characterizing U.S.-Soviet relations during his presidency.

While some earlier summits ended with major nuclear-weapons agreements, this one is expected to conclude with Reagan signing minor accords and leaving arms negotiations to the arms talks under way in Geneva.

"This is the first summit in six years, so it should not be compared to the kind of summit we had in the 1970s because those came at the end of extremely intensive periods of negotiation," said Helmut Sonnenfeldt of the Brookings Institution, an adviser to Nixon.

Reagan is starting a new chapter in another sense -- the Gorbachev era, which could stretch to the end of the century, has just begun. While six U.S. presidents have preceded Reagan to the summit during the last 30 years, only two Soviet leaders dominated those meetings: Leonid Brezhnev, who attended five, and Nikita Khrushchev, who held four.

This meeting also could mark the begining of a new phase in superpower summitry if Reagan and Gorbachev agree to hold a second meeting, or regular summits, as Brezhnev once proposed. The 10 summits since World War II were generally held at haphazard intervals, except for three consecutive meetings in the Nixon era. Reagan has endorsed the idea of another meeting.

Summits have produced varied results, ranging from the ill-fated Paris meeting that collapsed in 1960 after the Soviet Union shot down a U.S. U2 spy plane to the major strategic-arms accords signed in the Nixon, Ford and Carter years.

The emphasis has changed, too. Summits involving Presidents Dwight D. Eisenhower and John F. Kennedy stressed reducing international tension caused by such controversies as reunification of Germany and access to Berlin. By the 1970s, arms control was the prime topic.

Paralleling growth in superpower nuclear arsenals, there has also been a shift from the emphasis in Eisenhower's presidency on multilateral summits, which included some European allies, to exclusively bilateral U.S.-Soviet meetings.

In contrast with the Geneva summit of 1955, when Eisenhower stood shoulder-to-shoulder with the leaders of Britain and France, the allies have been left on the sidelines in 1985 and are to be briefed by Reagan in Brussels afterward.

The shift to emphasizing strategic arms control on the summit agenda was highlighted at the hastily-convened 1967 meeting at Glassboro State College in New Jersey between Johnson and Soviet premier Alexei Kosygin.

There, then-defense secretary Robert S. McNamara tried to persuade Kosygin that Moscow's antiballistic-missile system threatened to widen the arms race. The discussion eventually led to the 1972 Antiballistic Missile Treaty and the SALT discussions on limiting strategic arms.

Nixon met with Brezhnev three times, and summits became more ambitious undertakings, producing major strategic-arms agreements. Nixon also tried to use summits to extricate the United States from Vietnam and pressure the Soviets with his diplomatic opening to China, but the strategy was undermined by the Watergate scandal and Nixon's resignation in August 1974.

Later that year, it fell to Ford in the eastern Soviet city of Vladivostok to reach a tentative agreement with Brezhnev that laid the groundwork for SALT II. Jimmy Carter signed the SALT II treaty in Vienna in 1979, but the Soviet invasion of Afghanistan in December that year crushed any prospect of Senate ratification.

The Reagan administration has played down the value of a "get acquainted" meeting, but history shows numerous examples of informal summit contacts between leaders that proved significant. Gordon R. Weihmiller, in a forthcoming study of U.S.-Soviet summitry for Georgetown's Institute for the Study of Diplomacy, concludes that these moments have been "favorably noted by every president involved in the postwar summit experience with the Soviets."

For example, in Geneva in July 1955, Eisenhower mingled with the Soviet delegation while walking to a cocktail lounge. Although Soviet Premier Nikolai Bulganin had shown interest in Eisenhower's "Open Skies" plan for arms inspections, Khrushchev told the president as they strolled that he disagreed with the premier.

"There was no smile in his voice," Eisenhower later recalled. "I saw clearly then, for the first time, the identity of the real boss of the Soviet delegation."

Nearly two decades later, Nixon received an unexpected midnight "tirade" on the Middle East by Brezhnev when the two met in California in 1973. "This testy midnight session was a reminder of the unchanging and unrelenting communist motivations beneath the diplomatic veneer of detente," Nixon later wrote.

Sonnenfeldt said Reagan must convince Gorbachev that he is still a strong president and show "that he does have authority, he does have the capacity to act. He must avoid Gorbachev and his associates carrying away from Geneva the impression that this is a lame-duck presidency."

The hazard of a wrong impression is often cited in the June 1961 meeting between Kennedy and Khrushchev in Vienna, perhaps the low point in post-World War II summits. It followed the Bay of Pigs debacle in Cuba and, as Kennedy later remarked, was a "very sober two days."

Khrushchev concluded that he could successfully challenge the new U.S. president with an audacity that led to the Cuban missile crisis a year later.