Worldwide, marijuana (cannabis) is a widely used drug. The incidence of marijuana smoking is increasing and is second only to tobacco as the most widely smoked substance in the general population. It is also the second most commonly used recreational drug after alcohol. Some adverse effects of marijuana smoking have been documented; however, the number of studies on the pulmonary effects of marijuana in individuals with leukemia is limited. In our case series, we report on 2 men with acute myeloid leukemia with miliary nodular lung patterns on computed tomography of the chest due to heavy marijuana use. We also report on 2 patients with acute lymphocytic leukemia who had a history of smoking marijuana and then developed lung opacities consistent with mold infection.