Objective: Many adolescents struggle to access appropriate mental health care due to structural or psychological barriers. Among those who do access an intervention, retention is a pressing concern. As a result, adolescents are less likely to benefit from an intervention. Although traditional barriers to participation (e.g., location, cost) are hypothetically reduced or removed in internet interventions, low retention is still common, particularly in unguided programs (those not involving a clinician). It is therefore key to determine what factors are associated with dropout in digital mental health interventions with adolescents both within and beyond the context of research studies. Methods: We compare completion rates from two projects evaluating self-guided, online single-session mental health interventions (SSIs) for adolescents. One was a randomized controlled trial (RCT) in which participants were paid for participation. The other was a program evaluation project in which participants were not paid for participation. We additionally compare SSI completion rates across various demographic groups and across baseline hopelessness levels. Results: There was a statistically significant difference in SSI completion status between the RCT (84.75% full-completers) and the program evaluation (36.86% full-completers), X2 (2, N =2436) = 583.5, p < .05. There were no significant differences in the baseline hopelessness scores across completion statuses in either study. There were no significant differences in full-completion rates across demographic groups in either project. Conclusion: Adolescents may be more likely to complete a brief digital mental health intervention if they are paid for participation. Additionally, it is possible that the brevity of SSIs reduces demographic disparities related to retention by minimizing the time required to complete an intervention.