Background. Rates of psychological distress among adolescents have increased in recent years, which has brought attention to the worsening mental health crisis. Increase in mental health service demands and massive shifts in service delivery models, in part due to the COVID-19 pandemic, has led to changes in adolescents’ help-seeking behaviors and attitudes toward digital mental health tools. We aimed to examine 1) whether adolescents with higher levels of psychological distress were more likely to seek mental health support; 2) adolescents’ reasons for not trying online tools for mental health support. Methods. We utilized data from three annual cohorts of adolescents aged 12-17 (n=847 in 2019; n=1,365 in 2020; n=1,169 in 2021) recruited as part of the California Health Interview Survey, a statewide representative sample. We estimated two logistic regression models to examine the likelihood of using mental health support, as a function of psychological distress, and survey time point as a proxy for time, while controlling for sociodemographic characteristics. Use of professional help and use of online tools were entered as dependent variables separately in the two models. We also analyzed weighted frequency and percentages of adolescents’ self-reported reasons for not trying an online tool stratified by adolescent-reported distress level. Results. The rate of adolescents reporting elevated psychological distress ( >30%) was significantly higher than the rates of those reporting use of using professional or digital support (< 10%). Rates of adolescents' use of professional help and online tools did not significantly change over time (2019-2021), after controlling for sociodemographic variables, ps > .05. A higher level of distress was associated with a greater likelihood of using professional help (OR=1.11, 95% CI=1.05—1.16) and online tools (OR=1.18, 95% CI=1.10—1.26). Of those experiencing high levels of distress, adolescents’ main reasons for not using an online tool included a lack of perceived need (19.24%), a lack of perceived helpfulness (15.72%), and a desire for handling problems themselves (16.36%). Discussion. Unmet mental health needs indicated a large service gap. Lack of perceived need was the top reason for not using an online tool among adolescents with elevated levels of distress. Effective marketing and dissemination efforts tailored to adolescents may increase mental health need recognition and subsequent initiation of mental health support.