THEY SAT THERE in the restaurant at Tysons Corner, the two of them, both with long blond hair, youthful, pretty faces, and they looked to be 15 or 16 years old at most. They had come out of hiding. They were going public. They had rehearsed the gestures in front fo private mirrors and they had learned how to do It.

They held the superlong, filter tipped cigarettes between their fingers, flicked the ashes off into the ashtrays without spilling them on the table-cloth or in their Cokes, and it up the next cigarette on the first try. They were so busy puffing and lighting and posturing with their cigarettes that they barely had time to talk to each other. They had arrived. They were sophisticated. They were pathetic. Theirs is a generation that ought to know better.

Years ago, before the first surgeon general's report on smoking came out, smoking was good for you. If you were a teen-age girl, it made you more attractive. It gave you flair. It fave you something to do with your hands, other than bite your nails. There was a vague suspicion around in those days that smoking might not be terrific for your health, but it was only a suspicion. Parents who tried to prevent their kids from smoking did so simply because the kids were kids and smoking was something grownups did.

There were parents who told their teen-age daughters that smoking wasn't ladylike, but being ladylike had lost some of its bloom by then, and besides, all the girls were smoking. We smoked in high school and we redoubled our smoking in college, and we smoked through pregnancies and smoked around out babies because no one could really prove to us that smoking was all that bad.

For every report that said smoking increases your chances of cancer and heart disease, there emerged another report challenging the evidence and the condlusion. There was a time when you could smoke and find some report that would tell you it wasn't that bad if you didn't smoke too long, or some other rationalization.

There are now 30 million ex-smokers in the United States and for all of us there came a moment of decision, when the price of smoking became too high and the chances we were taking with our health were too great. For some of us it was waking up in the mornings coughing, for others it was going to the doctor and seeing the black marks on the chest X-rays. Some of us had kids who implored us to quit. They were hearing in the homes the same hacking cough they were hearing on television commercials, only it wasn't some actor coughing. It was their parents. There was no question that smoking was dangerous to our health. We quit.

Quitting became a status symbol. It meant you had willpower. You were a person of character. You no longer smelled like an ashtray. You felt a little superior to the next guy. After all, you were going to live longer.

Despite all this, the number of smokers and the numbers of cigarettes produced annually went up. Statistics on young smokers became alarming. A new generation of smokers was coming along. The same generation that had begged us to quit was now smoking. There are now 6 million teen-agers smoking regularly. The percentage of girls aged 12 to 14 who smoke has increased eight times in the past 10 years. More than 60 percent of the teen-agers smoke regularly.

These are teen-agers who have grown up with the knowledge that smoking can be harmful, that it can cause cancer and emphysema and all sorts of debilitating diseases. These are teen-agers who have studied about the dangers of smoking in junior high school health classes, and yet they are smoking. Nothing bad is going to happen to them.

It has been 15 years since the first surgeon general's report on smoking was released, and yesterday Health, Education and Welfare Secretary Joseph A. Califano Jr. released another such report. Once again, with new and more detailed information, the government has determined that smoking is harmful. It is warning us that it is definitely more harmful than previously believed to teen-agers and to women and to unborn babies.

And once again, the industry-backed Tobacco Institute is attacking the srgeon general's report. The institute is admitting that cigarette consumption may be down. You can tell the industry is runnng scared. It is, as usual, trying to spread confusion about all the statistics linking smoking to cancer and other diseases. But this time it has stooped to quite personal attacks against Califano.

Tobacco Institute representatives have taken to the airwaves with the same set little patter, labeling Califano a reformed three-pack-a-day smoker who is operating with the "zeal of a reformed sinner." Bill Dwyer of the institute intoned into the mikes at a press conference Wednesday that Americans ought to beware of Califano giving up liquor and other more intimate activities. They are saying that smoking is a matter of freedom of choice, that people should be able to make up their own minds whether to smoke or not, and they are trying, in other words, to pervert a major public health problem into a civil rights issue.

The Tobacco Institute is attacking Califano as a zealot, somebody who would force his own personal preferences on others. Califano smoked three packs a day, and he knows what it feels like to wake up in the mornings and he knows what it feels like to quit. He is, after all, the country's chief public health officer, and he is using the best tools that he can find to alert the public anew to the dangers of smoking. He is stressing new information available about the dangers of smoking to teen-agers, who haven't gotten the message in the other ways we've tried, who are not able to make up their own minds about smoking.

The Tobacco Institute has seized upon an HEW memo describing the release of a new report on smoking as a "media event." Turning a "serious health question" into a "publicity stunt" is "shabby," the institute's Patricia Drath declared on "Panorama" yesterday. Of course the release of such a report is going to be a media event. What better way to alert the public about the dangers of smoking than through publicity?

The Tobacco Institute lobbyists are wrong in labeling smoking a health question. They appear to be the only ones who have any questions left about it. But they are right about one thing: there has been some very shabby behavior exhibited in connection with the latest smoking report.