Tobacco smoke and marijuana smoke have some things in common. For example, they are both “smoke.” Yet it appears there are some significant differences between the two, according to a study conducted by University of California San Francisco researchers.
For starters, one causes lung problems and the other doesn't.
Researchers found no link between marijuana smoke and emphysema, or any of the other pulmonary problems associated with cigarettes. In fact, some light marijuana users had higher lung function that nonsmokers.