Marijuana and lung cancer Smoking marijuana may be associated with an increased risk of developing lung cancer. Additional research is needed to fully understand the long-term health effects of marijuana smoking and how it affects a person's risk for lung cancer. However, researchers know that marijuana smoke contains many of the same harmful chemicals and compounds found in tobacco smoke. The issue is made more complex because many marijuana users also smoke tobacco, so it can be difficult to determine the cause of diseases they develop. For these reasons, physician researchers believe there still is cause for concern about smoking marijuana and lung health.