The most comprehensive collection of modern French and Russian art ever seen in this country has opened here to delighted crowds, despite a fresh display of what is surely the most durable of Soviet art forms -- censorship.

While French diplomats and organizers fume over last-minute deletions from the "Moscow-Paris, 1900-1930" exhibit ordered by the regime's conservative cultural watchdogs, thousands of well-connected Soviets are pouring excitedly through sweltering second-floor galleries of the Pushkin Fine Arts Museum near the Kremlin to see masterworks of modern art by their own countrymen that have been banished from view here for more than 50 years.

More than 2,500 paintings, sculptures, posters, concert programs, architectural sketches, art crafts and books dating from the tumultuous first three decades of this century are packed into 15 halls and arcades at the museum. Crowds form long lines outside daily, clutching expensive two-ruble tickets for a strictly controlled 2 1/2-hour tour of the collection, which opened last Wednesday.

The exhibit points up the strong connections between French modernists and turn-of-the-century Russian artists who flowered into the brilliant Russian school of abstraction before the 1917 revolution and which the communists throttled when Stalin took full control of the country a dozen years after the czar was driven from power.

About half of the Russian paintings on display have never been seen publicly in the U.S.S.R. The works had fallen victim to the "socialist realism" forms imposed by Stalin to emphasize, in accordance with Lenin's teaching, "the partyness" of all art for the Soviet masses. Now, the venerable walls of the Pushkin seem afire with the luminous and challenging abstractions of Marc Chagall, Vasily Kandinsky, Kazimir Malevich, Vladimir Tatlin, Lyuba Popova and others whose works for decades had been consigned to museum basements.

The exhibit is a near-replica of the widely hailed "Paris-Moscow, 1900-1930" show at Paris' Georges Pompidou Center in 1979. But it is not identical, and thereby hangs one more tale of Soviet censorship. As in virtually every other major international art exhibit here over the years of detente and before, the state refused to allow some works to be hung, or distorted and limited the information included in the official catalogue, outraging the French and bringing unusual recriminations at the official opening.

It was not only that several Western owners refused to allow canvases to be sent here for the show. In 1979, at the French showing, there had been some criticism because, at Soviet insistence, no mention was made of the fate of artists arrested and killed during Stalin's purges of the 1930s. For the show in Moscow, the Soviets wrangled over a number of abstract canvases, refused for weeks to allow a review of the full catalogue and then made some last-minute deletions from the collection after a private tour by Soviet cultural chief Pyotr Demichev. An accurate list of what was expunged is still not available, though it appears that all major canvases brought in from the West survived.

French complaints center chiefly on the catalogue. The hated name of Leon Trotsky, second most important figure in the Bolshevik takeover and later Stalin's defeated rival for power, was struck from an essay in the catalogue. The Soviets also censored a mention of the 1930 suicide of Vladimir Mayakovsky, hailed here as the principal poet of socialist realism. His death is considered by non-Soviet art experts to mark the end of the period of experimentation with modernist art forms and the full triumph of socialist realism, which more or less continues to this day.

But the tampering raised a ruckus in France, where, it has been reported, the French culture minister, along with other important cultural figures, canceled plans to attend the opening. Paris' ambassador to Moscow, Henri Froment-Meurice, said at the formal opening that the show "could have been even better, if, to [our] great regret, modifications had not been made at the last moment by the other party."

Pompidou Center director Georges Pontus-Hulten complained as well about "non-respect for the agreement we signed," and is said to have added: "This stems from our different ways of viewing history: We believe that an event, a work or a man [who] once existed cannot be denied."

Dozens of the Best Soviet artists and writers emigrated after the revolution as the shape of the new regime became clearer. Kandinsky and Chagall are perhaps the best-known of the artists who continued working abroad, but many poets and writers left seeking intellectual freedom. The exhibit's explanations, while sparse, give a flavor of how the Soviets handle this exodus. In speaking of the writers whose portraits or book jackets are included in a part of the exhibit, the Soviet organizers wrote: "The best representatives of Russian literature decisively supported the revolution, giving their talents and knowledge to the people." While displaying some works of Boris Pasternak, Maria Tsvetaeva, Osip Mandelshtam, Sergei Yesenin and Nikolai Gumilov, the exhibit offers no word of their fates: Pasternak died in official disgrace, Tsvetaeva and Yesenin committed suicide, Gumilov was shot by the Bolsheviks, Mandelshtam died in the camps.

But for the crowds wandering through the exhibit, this unpleasant reality scarcely registers. What is important is that so much, however disturbing and stark, is gathered in one place. Many visitors can be seen taking notes, since the two-volume hardback catalogue, lavishly illustrated and priced at 16 rubles, 90 kopecks ($22.80), was published in a sharply limited edition of 25,000 and already has become a collector's item and likely will be an expensive blackmarket commodity.

The exhibit, which is expected to be viewed by more than a million people before it closes in four months, shows the ferment brought back here by successive waves of Russians who went to Paris to steep themselves in the Impressionist and post-Impressionist French schools. There are the French modern masters -- Matisse, Degas, Modigliani and others -- and the seminal influence of Picasso to be seen everywhere. But in time, the Russians reached out through Expressionism, Fauvism, Cubism and myriad other schools to explore Suprematism under Malevich's lead, or take up the endless abstractions of Kandinsky, Tatlin and others.

But as the exhibit also makes clear, shortly after Lenin and his followers came to power, the impulsive glorification of their achievement hardened into something different: The propagandists present among the revolution's chroniclers became all-important, and soon there was no room for anything else in Soviet art. Those who did not leave were forced into other fields. Malevich became inactive; Tatlin, whose monument to the Third International would have raised an ironwork spiral 1,300 feet into the air with rotating geometric glass buildings suspended inside for public meetings, meals and concerts, took up scenic design and found an almost obsessive new interest: aerial flight.

Their works gradually disappeared from public view, and a number of small museums that had catered to Russian and French modernists were closed.

The repressive tendencies of the revolutionaries were there from the beginning, and "Moscow-Paris, 1900-1930" makes this clear, quite apart from the censorship dispute accompanying its opening. One example suffices: a bas relief by S. E. Cherinishev, dating from 1918 and proposed for the facade of a public building. It shows a sack of grain and bears the famous inscription "Kto ne rabotaet, tot, ne est." -- "He who does not work shall not eat."

Now, as then, it is the Soviet state which decides what is worthy work.