Ordered to pay more than $15 billion in damages to Quebec smokers in a landmark case, three major Canadian cigarette manufacturers are being heard by the Quebec Court of Appeal this week.

 Imperial Tobacco, JTI Macdonald and Rothmans, Benson & Hedges are fighting to invalidate the ruling of a June 2015 case.

Their argument is essentially that smokers knew the risks of using a legal, but dangerous, product.

"We believe we have strong arguments in this case, and we believe the judgment should be overturned in its entirety," said Michael Klander, ‎Director of Corporate Affairs at Rothmans, Benson & Hedges.

In his ruling, Justice Brian Riordan of the Superior Court ruled that the three cigarette dealers had 'put their profits before the health of their customers,’ calling their actions ‘particularly reprehensible.’

The companies were targeted by two separate lawsuits heard at the same time that were filed in 1998 and only went to trial in 2012.

The three companies were ordered to pay billions to 100,000 Quebec smokers who were victims of cancer and emphysema, as well as those who became addicted to nicotine.

The case hinged on the misleading advertising and denouncements of scientific studies that tobacco companies used from the 1950s to 1980s to pretend smoking was not a danger to health. 

Anti-tobacco activists defended Riordan's ruling.

"Did tobacco companies do something wrong? Absolutely," said Canadian Cancer Society Senior Policy Analyst Rob Cunningham.

"Was there massive evidence they did so, in terms of their own internal documents and expert evidence? The tobacco companies fought 14 years for this case to get to trial, the trial took two-and-a-half years, there was copious evidence of their wrongdoing, the court found a finding and we hope this case will be upheld on appeal as soon as possible so payments can begin to victims."

Quebec Council on Tobacco and Health Executive Director Mario Bujold said manufacturers had misled generations of smokers on the risks that came with tobacco.

"They lied to the population for more than 50 years," he said.

"The judge said in his judgment that they made profit throughout these years. They didn't respect their own clients with the information they should have given to them."

Some 76 witnesses came forward during the trial and nearly 43,000 documents were entered into evidence, including internal tobacco company documents that showed smokers didn't know or understand the risks associated with cigarettes.

If the lower court's ruling is upheld, smokers who were diagnosed with cancer could receive up to $100,000, while those who developed emphysema could get up to $30,000. 

However in most cases, the money would go to their estates.

The same three cigarette companies are also being sued for $60 billion by the Quebec government in an effort to recover health care costs related to treating smokers.