Certainly the road to Russia was paved with good intentions, but "The Soviet Union -- Seven Days in May," a potentially monumental CBS News special at 9 tonight on Channel 9, proves too often diffuse and cluttered, as much runaway as breakthrough.

Even so, the program is absolutely worthwhile as a viewing adventure -- an eye-opener and a must-see, however flawed the execution.

There is enough fascinating material here for five normal documentaries, and you may begin to wish CBS had made one of them. The total immersion technique that worked so well in "48 Hours on Crack Street," about drug abuse in America, doesn't perform so strongly here. The viewer is led on such a frenetic chase that it's a little like being on a whirlwind bargain tour. If it's Tuesday, this must be Irkutsk.

Despite the title, and the fact that CBS fanned nine correspondents and 50 crew members throughout the U.S.S.R. from May 20 through May 26, the documentary is not arranged in chronological, "week-in-the-life-of" order. It means to be much harder edged than that, and it has a theme, supplied by Soviet leader Mikhail Gorbachev. The theme is "glasnost," or openness, hammered into every cranny of the broadcast with the relentlessness of an indoctrinator.

When it's all over, we still can't be sure if there is really much more to Gorbachev's glasnost than there is to the latest miracle ingredient that causes a laundry detergent allegedly to be "new and improved." But the subject isn't allowed to rest for long.

"That was then, this is now," the broadcast keeps saying. Tom Fenton, after hearing blunt remarks from a boy scout instructor turned black marketeer, notes, "Not long ago, he'd be in Siberia for saying that." Bernard Goldberg marvels that CBS cameras are allowed to record a drug bust for the first time ever. Fenton proclaims that a trip aboard a mine sweeper marks "the first time western journalists have been aboard a Soviet warship of any kind with a camera," then concedes the Russians did a last-minute paint and fix-it job to shape up the ship.

When something is not compared to the U.S.S.R. as it used to be, it is compared to the United States as it is. Lesley Stahl, reporting from a Soviet hospital (more properly Susan Spencer's beat), says Soviet doctors brandish "needles much thicker than the ones we use," and Bruce Morton, observing the morning meeting at a steel mill in Volgograd, calls it "Hill Street Blues -- with a difference." Such provincialisms are not becoming.

Executive Producer Lane Venardos keeps the screen swimming in images, many of them vital and compelling. Yet the most valuable parts of the program seem to be simple, provocative conversations. Ed Bradley has a humdinger with Genadi Gerasimov, slippery Soviet spokesman. Referring to the much-discussed and very leaky U.S. Embassy in Moscow, Bradley says, "They say the whole thing is a bug," and Gerasimov chuckles, "Maybe." Bradley is at his best and boldest in this interview, though he appears to be under the impression that Japan has failed to rearm only because it doesn't feel in the mood.

Dan Rather anchors the program with his usual surpassing authority, but isn't seen nearly enough. He is relaxed yet probing during a session with a magazine editor known as "the little flame." Rather wrote a piece for the magazine and is seen, in a jean jacket, buying a copy at a newsstand. Later he demonstrates a curious kind of mineral water vending machine (to each according to his thirst, but in the same glass) with the very American preface, "Get a load of this."

The separate pieces that make up the program are all modular and tumble out in no particularly logical order -- or rather, at least in the beginning of the show, in the wrong order. Venardos and his bosses apparently wanted to plunge the viewer into the kinetic maelstrom as quickly as possible. So they open with a very busy piece by Fenton on private enterprise in Estonia, which Fenton then admits is atypical anyway. This is followed by reports on dope ("Tbilisi Vice" is the cutesy title for that one), heavy metal rock, the boring mine sweeper and, finally, a first-rate encounter between Diane Sawyer and Boris Yeltsin, "The Boss of Moscow" and a member of the Politburo, who shows Sawyer around his office.

Sawyer reminds Yeltsin of Khrushchev's famous threat to the West, "We will bury you." He says, "Nobody's saying that now."

Here the documentary finally gets to a truly informative introductory moment, the TV equivalent of an "establishing shot" in a movie, but it's five segments in. It lets us know where we are and what the program is all about, and something of how the Soviets now are ready for what Rather calls "the most open examination of Soviet life my colleagues and I have ever been able to attempt."

There are some odd priorities. Very little attention is given the plight of Soviet Jews and the "refuseniks." A curious conceit of the broadcast is that the more rock music in a society, the more "open" it must be, and the footage of rock wailing is oppressively excessive (oh, but filled with fractious motion -- producers like that).

One piece, ostensibly about those who have fled the Soviet Union only to return later, seems completely irrelevant to the topic, since it concerns a pair of musicians who found out they couldn't make as much money in New York as they thought they could. A CBS Records producer is among those interviewed, making the segment not only pointless but a trifle tacky.

Rather and his colleagues scrupulously take note of the limitations of glasnost that they experienced. Here and there local authorities balk at the presence of cameras; they don't want them taping a long line of customers waiting to buy food, nor a beggar in the street. Any number of incidents captured on tape proffer insights into both modern political realities and the time-worn Russian character.

And there are stunning visual moments, like a montage of grim faces at a Soviet cemetery, only recently opened to the public, where the remains of Chekhov, Gogol and Khrushchev are buried. "Seven Days in May" is most obviously not a case of a documentary that attempts to stretch thin material out to length. CBS came back with much more than two hours could hold (and additional reports have aired on other regularly scheduled broadcasts). They try to cram in as much as they can, and sometimes the cramming hurts.

One small irony is that with all the man- and womanpower CBS sent to Moscow, it didn't capture the landing of a small plane by an amateur pilot in Red Square, which occurred just after the CBS visit. NBC News had "exclusive" tape of that -- bought from a home video enthusiast on the scene.

"Seven Days in May" flies by at a breathless zip. There simply aren't enough solid, contemplative respites, and the bits and pieces don't add up to a sufficiently illuminating wide view. But then, this is the first really substantial documentary of the glasnost era (however long that may last) and it may be unfair to expect too much of it.

"When a superpower stirs, the world holds its breath," Rather says near the close. CBS News is a journalistic superpower itself, albeit a humbled and struggling one, and it bestirred itself mightily to come up with this earnest dazzler. Too much dazzle can be a dispiriting thing, however, and instead of shining as bright a light as possible on its subject, "Seven Days in May" is too often more intent on shining it right in our eyes.