Objectives
The increasing prevalence of drug use in the Republic of Korea has emerged as a significant social concern. This study applied the extended theory of planned behavior to investigate the factors influencing intentions to use drugs among young adults (aged 20–30 years) in the Republic of Korea. The study integrated personal traits—specifically, impulsivity, sensation seeking, and self-efficacy—into 2 core theory of planned behavior constructs: attitudes and subjective norms. The principal aim was to improve the prediction of drug use intentions by incorporating these variables. Methods: Data were obtained from the 2023 National Survey of Drug Harm Perception, which sampled 1,500 individuals aged 19 to 39 years. Hierarchical regression analysis was employed to assess the influence of psychological and social factors on intentions to use drugs. Results: In the primary model, age emerged as a significant predictor of drug use intentions (R2 =0.01). The secondary model showed that positive attitudes toward drugs, subjective norms, and lower self-efficacy significantly increased drug use intentions (R2 =0.23). In the final tertiary model, the addition of sensation seeking and impulsivity further amplified these intentions (R2 =0.25). Conclusion: The findings underscore the pivotal roles of attitudes, subjective norms, and selfefficacy in shaping intentions to use drugs. Sensation seeking and impulsivity were found to further elevate vulnerability. Effective prevention efforts must address both psychological traits and social influences. Future research should examine the long-term behavioral outcomes associated with these factors.