INTRODUCTION: Many U.S. states expanded the generosity of Medicaid insurance coverage of tobacco dependence treatment over the last fifteen years, but little is known about how coverage impacts cigarette smoking, especially for individuals with substance use disorder. METHODS: Data are from the 2009 to 2018 National Survey on Drug Use and Health and include Medicaid beneficiaries 18-64 years old with past year substance use disorder who smoked at least 100 cigarettes in their lifetime. Outcomes were smoking cessation, nicotine dependence, and number of cigarettes smoked per month. Difference-in-differences models were estimated for smoking behavior by state and year of comprehensive tobacco dependence treatment coverage, estimating multivariable linear probability models, adjusted for sociodemographic characteristics, co-occurring mental illness, and area-level provider supply. All data were analyzed in 2023 and 2024. RESULTS: Rates of nicotine dependence among individuals with past-year SUD increased slightly between 2009 and 2018 among individuals living in states with comprehensive tobacco dependence treatment coverage (55.6% to 58.6%) and changed little among individuals living in states with no or partial TDT coverage (60.0% to 59.5%). Quit rates increased for individuals with substance use disorder during this time, with no differences by comprehensive tobacco dependence treatment coverage. In adjusted models, no significant association between comprehensive Medicaid tobacco dependence treatment coverage and smoking behaviors was identified (e.g., cessation: β= -0.02, CI=-0.08, 0.04). One-year lagged outcomes and sensitivity analyses accounting for the differential time of initiation of state policies demonstrated similar results. CONCLUSIONS: Comprehensive tobacco dependence treatment coverage had no differential effect on smoking cessation among ever smokers with or without substance use disorder, and its expansion was not associated with changes in smoking behaviors for Medicaid beneficiaries with substance use disorder. Other multilevel interventions may be needed to impact smoking cessation rates, such as awareness and education campaigns of expanded tobacco dependence treatment coverage benefits, and interventions that reduce social and structural barriers to treatment.