Research suggests those who smoke are 80 percent more likely to be hospitalised and significantly more at risk of dying from Covid-19 than non-smokers.
The study by Oxford University is the first to look at both observational and genetic data on the relationship between smoking and coronavirus.
It found those who have one to nine cigarettes a day, are twice as likely to die.
Lead researcher, Dr Ashley Clift, has this message:
"Now is as good a time as any to reduce or quit smoking."
"And with things like Stoptober coming up it might play into that, you might encounter extra good if you do stop smoking."