Cannabis demand (i.e., reinforcing value) can be assessed using a marijuana purchase task (MPT; assesses hypothetical purchasing of cannabis at escalating prices) and has been related to use frequency, problems, and cannabis use disorder symptoms in adults. Cannabis demand has yet to be studied in adolescents, which can inform prevention and intervention efforts to reduce cannabis-related risks. The present study sought to validate the MPT with a sample of late adolescent lifetime cannabis users. Participants aged 15-18 years old (n = 115, Mage = 16.9, SD = 0.9) residing in a state with legalized cannabis use completed online assessments at baseline and 6-month follow-up. Convergent and divergent validity was examined, while principal component analysis was conducted to determine the factor structure and assess predictive validity. Three indices, Omax (i.e., maximum expenditure on cannabis), breakpoint (i.e., price suppressing consumption to zero), and alpha (i.e., degree to which consumption decreases with increasing price) were all significantly associated with cannabis use, consequences, craving, and expenditures and significantly differentiated low-risk users and high-risk users as measured by the Cannabis Use Disorders Identification Test-Revised (CUDIT-R). A two-factor solution reflecting amplitude (intensity, alpha, Omax) and persistence (breakpoint, Pmax) was observed. Both factors were associated with cannabis use and consequences in baseline regression models. At follow-up, persistence was associated with consequences; amplitude was not associated with either outcome. These findings provide initial evidence that the MPT is a valid measure for assessing cannabis demand among adolescents and can be used to understand mechanisms of adolescent cannabis use. (PsycInfo Database Record (c) 2022 APA, all rights reserved).