A new study from Columbia University's Mailman School of Public Health found that marijuana smokers were more likely to smoke cigarettes than non-marijuana users. The study came from a survey of over 35,000 adults taken in 2001/2002 and 2004/2005. People who reported using marijuana in 2001/2002 were three times more likely to have a daily cigarette habit in 2004/2005 than non-cannabis users. Marijuana users were also 4.45 times more likely to have a non-daily cigarette habit. Marijuana users were also less than half as likely to quit their smoking habits than non-marijuana users.
Now, it should be noted that this data is somewhat out-of-date. In 2005, there were zero states with legal recreational marijuana and only a few with medical cannabis. Those numbers have greatly increased since then, and the number of cannabis users therefore has also significantly increased in the past 13 years. And as the number of marijuana users has grown, the number of cigarette smokers has decreased.
So it's possible that there would be significant changes in this data if you were to conduct the same study today rather than over a decade ago.