Objective: To evaluate the association between abuse of and dependence on different psychoactive substances and the presence of anxiety disorders in a sample of young adults from a city in southern Brazil. Methods: Between 2007 and 2009, we carried out a cross-sectional, population-based study of individuals aged 18-24 years who lived in Pelotas, a city in southern Brazil. We evaluated anxiety disorders using the Mini International Neuropsychiatric Interview 5.0 (MINI), and use of psychoactive substances with the Alcohol, Smoking, and Substance Involvement Screening Test (ASSIST 2.0/0MS). We used Fisher’s exact test for univariate analysis, and Poisson regression models with robust variance for multivariable analysis. Results: The sample consisted of 1,560 young adults. The overall prevalence of abuse/dependence was 26.9% for alcohol, 24.9% for tobacco, and 7.3% for illicit substances. Individuals with agoraphobia had a 32% higher prevalence of tobacco abuse/dependence (prevalence ratio [PR] = 1.32 [95%CI 1.01-1.74]). Individuals with posttraumatic stress disorder (PTSD) or generalized anxiety disorder (GAD) had a 2.41-fold (95%CI 1.22-4.77) and 1.76-fold (95%CI 1.00-3.11) higher prevalence of illicit substance abuse/dependence, respectively. Conclusion: In this population-based sample, we found associations between GAD, PTSD, and increased prevalence of illicit substance abuse/dependence. In addition, individuals with agoraphobia seem to have increased tobacco abuse/dependence.