A jury in Missouri has awarded more than $20 million US in damages to the family of a woman who smoked Kool cigarettes for nearly 50 years.

The Jackson County judgment is the fifth largest ever given in the United States in a wrongful death lawsuit against a tobacco company. There have been 14 such jury awards to date.

Barbara Smith smoked Kool cigarettes for almost five decades before she kicked the habit in 1990. She died 10 years later of a heart attack at the age of 73, after developing heart and lung disease.

Jurors decided Wednesday that her relatives should get $20 million in punitive damages from Kool brands maker Brown & Williamson.

A day earlier, the same jury had set actual damages in the case at $2 million, but found Smith herself to have been 75 per cent responsible for those damages and the tobacco company 25 per cent at fault. As a result, the family will get $500,000 from that finding.

Lawyers for Smith's family had argued that she would not have started smoking or continued to smoke had she been fully informed about the harm cigarettes could do. They blamed the tobacco company for hiding evidence of those harmful effects from the public.

The company's lawyers said Smith's fatal heart attack could not be linked to her smoking, given that she was elderly and had high cholesterol, high blood pressure and diabetes.

Calling the damage amounts "grossly excessive," Brown & Williamson asked the judge in the case to set aside the jury's recommendation.

There are precedents for that to happen.

A judge in Los Angeles recently reduced a jury award for a 45-year-old smoker with lung cancer from $28 billion to $28 million. That suit was brought against Philip Morris USA.

Another California jury awarded $3 billion in a wrongful death tobacco lawsuit in 2001, but a judge reduced the amount to $100 million.