Aims: The Confidence Interval-Based Estimation of Relevance (CIBER) approach was used to assess the most relevant psychosocial determinants of both the intention to use cannabis and the intention to reduce or quit cannabis use among high school students. Methods: In 2017, 206 Dutch high school students completed questionnaires. Questionnaires measured cannabis use in the past six months, intention to use cannabis in the upcoming six months, intention to reduce or quit cannabis use in the upcoming six months, psychosocial determinants, and sociodemographic characteristics. The CIBER approach was used to estimate the relevance of determinants by calculating and visualizing confidence intervals for the means and correlation coefficients for intention to use cannabis as well as intention to reduce or quit cannabis use. Results: Cannabis use was reported by 28% (57/206), and 26% (54/206) had the intention to use cannabis. Risk perception, attitude, and the descriptive norm were evaluated as the most relevant determinants of the intention to use cannabis. Among cannabis users, 49% (28/57) had the intention to reduce or quit. Attitude and habit were evaluated as the most relevant determinants of the intention to reduce or quit cannabis use among cannabis users. Conclusion: Cannabis use was prevalent among Dutch high school students. Findings suggest that interventions aimed at preventing cannabis use among the general school population might best focus on the risk perception, attitude, and the descriptive norm, whereas interventions aimed at reducing cannabis use among cannabis users might best focus on attitude and habits.