With nearly $18 billion on the line, lawyers for Quebec smokers and Big Tobacco began their final arguments Monday, in a landmark case that has been underway for years.

Two groups representing an estimated 1 million Quebec smokers are suing three major Canadian tobacco manufacturers to recover health care costs associated with using tobacco products.

The two groups include those who developed serious illnesses as a result of tobacco use, and those who are unable to quit because they are addicted.

The smokers’ lawyers have argued that, for decades, tobacco companies lied about the health risks associated with smoking, marketed a product they knew to be addictive, and destroyed documents that might have proved otherwise.

On the other side of the argument, Imperial Tobacco spokesperson Eric Gagnon doesn't believe a company should be responsible for consumers’ decisions.

"We don't believe that the tobacco industry should be held responsible for personal choices that people made, knowing there were some health risks associated with smoking," he told CTV Montreal.

The lawsuit can trace its roots to 16 years ago, when two cases were filed. They were consolidated in 2005, but because of procedural issues the trial only began in March, 2012.

More than 27,000 documents were presented and 78 witnesses were called to testify over 234 days of trial.

Closing arguments could take weeks, and the verdict isn't expected anytime soon. However, no matter what this Superior Court judge rules, the case will likely be appealed up to the Quebec Court of Appeal and possibly even to the Supreme Court.

Jean-Yves Blais, who initiated the lawsuit on behalf of those who developed serious illnesses from tobacco, was 68 years old when he died from lung cancer in the summer of 2012. He picked up the habit at just 10 years old, and smoked more than a pack a day for 50 years.

“We didn’t know at that time smoking was dangerous,” Blais said before his death.

With files from CTV Montreal's Stephane Giroux and The Canadian Press