This study examined the association between current co-use of cannabis and cigarettes in the past 30 days, and subsequent cigarette discontinuation (past 30-day point prevalence abstinence) among U.S. adults with established cigarette use in the Population Assessment of Tobacco and Health (PATH) Study. Additionally, we investigated the impact of co-use on the subsequent discontinuation of all combustible tobacco products. A total of 26,381 observations contributed by 8,218 adults with established cigarette use (i.e., smoked ≥ 100 cigarettes in their lifetime, and currently smoking cigarettes every day or some days) from Waves 1-5 of the PATH Study were included in the analysis. Weighted Generalized Estimating Equations (GEE) models were used to evaluate the association between current co-use at baseline (Waves 1-4) with the outcomes assessed at the subsequent wave (cigarette and combustible tobacco discontinuation at Waves 2-5). Final models included: demographic characteristics (age, sex, race and ethnicity, educational attainment), behavior characteristics (intention to quit, internalizing symptoms, externalizing symptoms, substance use problems), and wave-pair. Over one-third (35.91%) of cigarette users self-reported co-use during the study period. Cannabis use among adults with established cigarette use increased over time. Co-use was associated with a decreased odds of cigarette smoking discontinuation at follow-up, after adjusting for covariates (aOR: 0.81; 95% CI: 0.72, 0.93; p=0.0018). Similar effect sizes were observed for discontinuation of all combustible tobacco products (aOR: 0.75; 95% CI: 0.65, 0.86; p<.0001). Cannabis use among adults who smoke cigarettes was inversely related to subsequent cigarette discontinuation, suggesting that co-use may reduce likelihood of successful tobacco cessation. Findings demonstrate that cannabis use may lead to lower odds of discontinuation among adults with established cigarette use; therefore, individuals that co-use cigarettes and cannabis may need additional tobacco cessation support. Notably, this study observed an increase in co-use of cigarettes and cannabis, emphasizing the need for researchers and public health programs to shift their focus towards understanding and addressing concurrent substance use among adults who smoke cigarettes.