- Adolescents with substance use disorders (SUDs) smoke cigarettes more than youth in the general population. Little is known about changes in smoking patterns during and after outpatient SUD treatment. We examined whether receiving SUD treatment had a differential impact on cigarette smoking behaviors of mild (<10 cigarettes per day [CPD]), moderate (10-19 CPD), and heavy (≥20 CPD) smokers (smoked on ≥60 days in the past 90). Our sample included 378 adolescents from the Cannabis Youth Treatment study, who were assessed at intake, and after 3, 6, 9, and 12 months. Results indicate that after controlling for the effect of changes in cannabis use, mild smokers decreased days of smoking during treatment and follow-up, whereas moderate and heavy smokers demonstrated a small decrease over treatment, and no change over follow-up. Heavy smokers demonstrated a slight decrease in CPD during the treatment phase. These results suggest that, whereas cigarette smoking may decrease for mild smokers while in SUD treatment, the addition of specialized smoking interventions may be necessary to effect change in cigarette smoking for moderate and heavy smokers.