TRENTON, N.J., JULY 26 -- The health warnings on cigarette packs don't protect tobacco companies from liability lawsuits by smokers, the state Supreme Court ruled today.

The decision runs counter to several federal appeals court rulings. Those decisions generally held that the warnings, ordered by the government in 1966, absolved tobacco companies from responsibility in smoker's deaths.

Industry lawyers promised to appeal.

Richard Daynard, a law professor at Northeastern University in Boston and chairman of the Tobacco Products Liability Project, called the ruling the ''most important positive development in tobacco litigation in the last decade.''

''This decision represents the consensus of scholarly opinion that these earlier decisions were wrong and it is very likely to be upheld by the U.S. Supreme Court,'' Daynard said.

Six of the justices concurred in the decision; one filed a partial dissent. The New Jersey high court also said that changes in a 1987 state product-liability law didn't rule out lawsuits filed before the law was passed. Tobacco company officials believed the law protected them retroactively from suits by smokers.

The ruling will allow a 1982 lawsuit, filed by Claire Dewey of Wyckoff, to proceed. Her husband, Wilfred Dewey, died in 1981 from lung cancer after smoking for more than 40 years.

Dewey had smoked Camels, Tareytons and Viceroys, and his wife filed suit against the makers of those cigarettes, RJ Reynolds Tobacco Co., American Brands and Brown & Williamson Tobacco Corp., respectively.

''We are unable ... to decide that as a matter of public policy, manufacturers of cigarettes should be immunized from liability for the harms caused by their products,'' the court opinion said.

''In this case, a New Jersey jury could decide that a cigarette manufacturer, rather than an injured party, ought to bear the cost of injuries that could have been prevented with a more detailed warning label than that required under the cigarette act,'' the opinion said.

Jim Fyock, an RJ Reynolds spokesman, said the ruling ''flies in the face of decisions in the Supreme Court of Minnesota and five federal courts of appeal as well as numerous rulings in state and federal trial courts.''

Those rulings had all held that the warning labels on cigarettes, and wide publicity about the health dangers of smoking, meant smokers were doing so at their own risk.