Chief executives of the once-defiant tobacco industry came before Congress yesterday contrite and conciliatory and made their strongest public admissions ever that smoking is hazardous and addictive.

Their statements were in vivid contrast to decades of public denials on those crucial issues, including sworn testimony before Congress at the April 1994 hearing that marked a historic turnaround in the national debate on tobacco policy.

The appearance was the most dramatic part of a campaign by the industry to repair its public image, which is seen as crucial as the companies try to fight an avalanche of lawsuits nationwide and win congressional approval of legislation that would grant it broad legal protection in exchange for huge payments and moves to curb youth smoking.

The proposed national tobacco settlement has become increasingly precarious in recent months, in part because of the release of embarrassing internal industry documents suggesting that the R.J. Reynolds Tobacco Co. targeted teenagers with its marketing efforts for decades.

"I believe it is immoral . . . unethical, as well as illegal to market to people underage," Steven F. Goldstone, chairman and chief executive of RJR Nabisco, the parent of Reynolds, told the House Commerce Committee yesterday.

Goldstone also acknowledged for the first time in a public forum that he believes smoking "plays a role in lung cancer" and Geoffrey Bible, chairman of Philip Morris Cos., admitted that "tobacco is a risky product."

Bible also said in his statement that "under some definitions, cigarette smoking is addictive.' "

Only Nicholas G. Brooks, chairman of Brown & Williamson Tobacco Co., quibbled on addiction, saying, "I personally would not use that term."

Industry observers said the statements indicated how much the debate over tobacco in the United States has changed. "For those who want the truth out about the industry, today was a big victory," said Mississippi Attorney General Michael Moore (D), one of the architects of the proposed national settlement.

As the hearing began, Goldstone, Bible and three other chief executives stood in a row before the powerful committee, raised their right hands and swore to tell "the whole truth." But several lawmakers questioned the industry's ability to be truthful and challenged past industry statements as lies.

One of the stiffest challenges came from Commerce Committee Chairman Thomas J. Bliley Jr. (R-Va.), traditionally one of the industry's staunchest defenders and a lawmaker considered crucial to approval of broad-based tobacco legislation.

"Frankly I was shocked by what I read" in the RJR documents about youth smoking, Bliley told the assembled executives. "These documents appear to contradict statements made by representatives of your company before this committee," he said, adding that the documents "have shaken my confidence that your companies care about the truth."

Still, the executives made clear that their new conciliatory spirit would only go so far: National legislation must include broad protection from lawsuits or they would not go along with it. Goldstone, for instance, argued for "a fair and overall resolution," saying that in the proposed settlement the companies had agreed to give up some of their constitutional rights, including advertising on billboards and, in some cases, to adults.

"But in order to do that, we have to have some reasonable protections," Goldstone said.

Goldstone was cut off by one of the industry's most vocal critics, Rep. Henry A. Waxman (D-Calif.). Waxman and other Democrats on the committee angrily took issue with the industry's demand for liability protections -- which is fast becoming one of the settlement's most controversial elements.

"We don't need the tobacco industry's blessing to do this," Waxman said at one point.

However, some Republicans, particularly from tobacco states, defended the industry and questioned several major tenets of the settlement. "This is not a settlement, this is a surrender of an industry to an anti-tobacco offensive" by the Clinton administration, attorneys general and wealthy trial lawyers, said Rep. Edward Whitfield (R-Ky.).

It has been just four years since tobacco executives testified before Congress, but it is a new era in terms of the tobacco landscape. Since then, the federal government has asserted authority to regulate tobacco; attorneys general and private lawyers have mounted lawsuits against the industry in 41 states, and since last year, the industry -- once invulnerable to legal attack -- has settled major lawsuits by agreeing to pay more than $30 billion.

At the 1994 hearing, a much more combative set of industry executives denied absolutely that their companies manipulated nicotine levels in tobacco products or that those products were addictive. Each executive in turn said he did not believe that smoking caused such diseases as cancer or that smoking is addictive.

James W. Johnston, then CEO of R.J. Reynolds, scoffed at the notion that the word "addiction" could be applied to cigarettes -- a central notion to then-Food and Drug Administration Commissioner David A. Kessler's efforts to regulate tobacco products. "Doctor Kessler's definition of addiction would classify most coffee, cola and tea drinkers as addicts -- caffeine addicts," Johnston said at the time. He said that smoking was a pleasurable habit like eating sweets or drinking. Yesterday, it was an entirely different panel of chief executives who appeared before Congress. The group included Laurence Tisch, co-chairman of Loews Corp., the parent of Lorillard Tobacco Co.; and Vincent A. Gierer Jr., chief executive officer of UST Inc., the nation's largest smokeless tobacco company.

As more lawmakers, including some of the industry's traditional supporters, have begun criticizing the proposed national settlement, the industry has become more aggressive in promoting it. Yesterday, industry executives, who rarely grant interviews, took their campaign to television, appearing on "ABC World News Tonight" and public television's "NewsHour With Jim Lehrer."

Also, at the hearing, Philip Morris's Bible promised that the industry would publicly release 33 million pages of industry documents collected by the state of Minnesota for its lawsuit against cigarette makers. The release, however, will not include documents that contain "competitively sensitive information," he said, or those that the industry maintains are protected by lawyer-client confidentiality.

As with the industry's other actions, the promise won mixed reviews. Bliley quickly commended the industry, but Matthew L. Myers, of the National Center for Tobacco-Free Kids, said "the documents without a road map" to interpret them "will only result in delay" in considering legislation. CAPTION: Tobacco company executives Laurence Tisch, Geoffrey Bible, Vincent A. Gierer Jr., Steven F. Goldstone and Nicholas G. Brooks take oath before testifying before House Commerce Committee about proposed settlement.