By Petra Bartosiewicz

For years it was the same routine: wake up, light a cigarette, inhale deeply and start the day. "I wouldn't even get out of bed without a cigarette," said John Palagonia, 53, of Massapequa, N.Y., who was a two-pack-a-day smoker for more than 20 years.

In 1989, Mr. Palagonia, who entertains at children's parties dressed as characters like Barney and Elmo, decided to quit. He turned to Nicorette gum to curb the cravings for a cigarette. The smoke savored between sips of his morning coffee was replaced with a peppery square. On breaks at work, driving his car, after dinner - all the times he had luxuriated in smoke - he would pop another piece.

"I got to the point that I was having problems with my teeth, and my jaw was killing me," Mr. Palagonia said. He eventually returned to smoking for a short time "to get off the gum." What ended up working for him was counseling, not a hit of nicotine.

A third of the nation's nearly 50 million smokers attempt to quit each year, according to the American Cancer Society, and that has made smoking-cessation products an $800 million business in the United States alone. The products include gum and patches sold over the counter; pills, inhalers and nasal sprays sold by prescription; and even more exotic products like nicotine-infused lollipops sold on the Internet.

Still, addiction to nicotine remains. The medical field has accepted that fact since the mid-80's, when the Food and Drug Administration approved, by prescription, products like gum to give would-be quitters a substitute comparable to cigarettes in price and nicotine content, but without other cigarette toxins.

Now some scientists and former smokers are voicing misgivings. No one disputes that cigarettes, which are laced with toxic additives like ammonia, pose far graver health risks than nicotine alone, but nicotine is also classified as a poison, and in recent studies it has been shown to break down into a substance that causes abnormal cell growth. In 2001, researchers at Stanford University found that nicotine speeds the growth of malignant tumors by stimulating the formation of the blood vessels that feed them, a process called angiogenesis.

Dr. John Cooke, the lead author of the Stanford study, said, "As long as people are using nicotine replacements properly, it's a win for all of us, if we can get people to stop smoking. But, I would urge people not to use it long term."

For people addicted to nicotine, using the replacement products properly can be difficult. A study financed byGlaxoSmithKline, the pharmaceutical company that manufactures Nicorette and other stop-smoking products, found last November that more than a third of nicotine gum users continued chewing beyond the 12 weeks recommended under F.D.A. guidelines.

"We estimate 36.6 percent of current gum users are engaged in persistent use," said Dr. Saul Shiffman, a company consultant and the study's primary author. Though the company says on its Web site that nicotine "may promote lung cancer," it insists its products are safe "when used as directed."

Even the companies that make nicotine-replacement products acknowledge problems with treating this particular addiction. Dr. Kenneth Strahs, GlaxoSmithKline's vice president for research and development in smoking control, said, "I wish we could tell you that if you took one piece of our gum it would be enough, but that's not the case. Nicotine addiction is a chronic relapsing condition."

When the F.D.A. approved over-the-counter sales of Nicorette gum and the NicoDerm CQ patch in 1996, sales of the two products soared. GlaxoSmithKline reported $578 million in global sales of over-the-counter nicotine replacements during 2003, down from $606 million the year before as other companies jockeyed for market position.

How effective these products really are remains a debate. Some ex-smokers and smoking-cessation experts oppose using nicotine at all when trying to quit. "It's like the difference between snorting cocaine and freebasing it," said Mr. Palagonia. He has neither smoked nor chewed nicotine gum for a decade now after years of meetings at Nicotine Anonymous, a 12-step program.

"The trick with getting off cigarettes is to stop delivering the drug," said Joel Spitzer, a smoking-cessation counselor and director of education at WhyQuit.com, an online support and education site that advocates quitting nicotine cold turkey.

Mr. Spitzer, who estimates he has counseled 5,000 individuals in stop-smoking clinics he has run in Chicago, says nicotine replacements keep ex-smokers in a protracted state of withdrawal.

Denise Henrie, a mother of four from Owasso, Okla., is familiar with that. Ms. Henrie, 43, tried and failed twice to quit smoking, using nicotine gum for more than a year. "You feel a little hopeless," said Ms. Henrie, adding, "I just don't want to be addicted to anything at all." She has slipped back to her pack-and-a-half-a-day habit, but she remains optimistic. A package of Nicorette sits in her kitchen pantry for a third try.

According to the American Cancer Society, fewer than 5 percent of smokers who attempt to quit each year succeed. Of those who do, the society reported last year, 91 percent quit cold turkey.

Some people succeed only after a long struggle. Jeanne Hutchinson, 59, began chewing nicotine gum in 1984, the first year it was available by prescription. "One of the happiest days of my life was when nicotine gum was allowed to be sold over the counter," said Ms. Hutchinson, a social worker in Chicago.

But, years later, she was still hooked on the gum. "I felt almost like a drug addict," said Ms. Hutchinson, who estimates the 12 pieces she chewed each day cost her more than $15,000 over the years, without curing her habit. Suffering from a receding gum line and worn molars, she joined WhyQuit last January and managed to stop using nicotine.

STILL, when she reached into her coat pocket a few months ago and found a long-forgotten piece of gum, it took all her willpower not to pop it into her mouth.

That may be why analysts say that demand for nicotine-replacement therapies is unlikely to wither anytime soon. "We see it as a market with tremendous potential, but efficacy-starved," said Devesh Gandhi, a research associate at Sanford C. Bernstein, adding that the market - for "a product that really works, that manages both the addiction and the side effects of the withdrawal" - is there for the taking.