The primary goals of this project are to examine whether use of cannabis alters brain cannabinoid type 1 receptor (CB1R) availability in females, and if severity of cannabis withdrawal is correlated with CB1 receptor availability. CB1R are widely distributed in the human brain and can be quantified using PET imaging with the radiotracer 11C-OMAR (Carbon-11-OMAR). The effects MJ use on brain CB1R have not been studied in females. The current study will enroll 10 female MJ users in an inpatient protocol that includes administration of smoked MJ, followed by monitored abstinence with daily behavioral assessments, and PET imaging with 11C-OMAR. PET data will collected in 10 matched controls for comparison. The proposed study is an important first step to determine whether localized CB1R changes in female MJ users help explain, and provide a neurobiological target for intervention. Results will increase knowledge of cannabinoid mechanisms of cannabis use and severity of dependence in females, an understudied population.