Cannabis is among the top substances used by individuals with PTSD. Research regarding the effects of cannabis use on PTSD symptomatology is largely contradictory and unclear, claiming both the improvement and worsening of PTSD symptoms concurrently. Furthermore, cannabis use disorder (CUD) is increasing in prevalence, due to recent legalization of recreational cannabis use across much of North America. To date, relatively little is known about correlates of comorbid PTSD and CUD (PTSD-CUD), as well as the impact of comorbid PTSD-CUD on various areas of mental health functioning. Individuals with PTSD routinely experience barriers to acceptable and effective treatment, which may be further exacerbated by the co-occurrence of CUD. Three distinct research studies utilized a nationally representative sample of adult civilians (≥18 years) collected during the National Epidemiologic Survey on Alcohol and Related Conditions III (NESARC-III; N = 36,309) in 2012-2013. The aims of the proposed project were threefold: (1) to examine the sociodemographic profile of individuals with PTSD-CUD, (2) to identify distinct cannabis use profiles among individuals with PTSD, and (3) to examine rates of mental healthcare utilization among individuals with PTSD who use cannabis. This nationally representative sample provides the opportunity to examine the complex relationships between PTSD and cannabis use in comprehensive detail. Comorbid PTSD-CUD represents an increasingly frequent disorder combination that appears to impact treatment course and outcome. Improved understanding regarding the relations between PTSD and cannabis use is fundamental to reduce disorder durations, resolve healthcare disparities, and improve treatment interventions for this complex population.