The use of psychoactive products by young adults is usually described as part of their exploratory identity development. This behavior is facilitated by social and structural contexts where these substances are perceived as legal and easily accessible. While the motivations for initiating and continuing the use of tobacco and alcohol are well- documented, the same cannot be said for e-cigarettes. The primary objective of this systematic review was to describe the reasons for initiation and continuation of e-cigarette use among adults aged 18 to 30. A secondary objective was to categorize these reasons into intrinsic (i.e., personal motivations) and extrinsic factors (i.e., sociocultural or structural influences). Searches were conducted in MEDLINE, Scopus, SocINDEX full text, PsycArticles, PsycInfo, Psychology and Behavioral Sciences Collection, Cochrane Library and gray literature. Studies involving humans, published in English or French up to June 2024 were eligible for inclusion. After removing 594 duplicates, 1,123 articles were screened by title and abstract, with 37 articles published between 2015 and 2024 ultimately included in the review. These comprised 21 cross-sectional studies, eight qualitative studies, six crosssectional analyses of cohort data, one cohort study and one mixed methods study. The appeal of e-liquid flavors emerged as one of the most frequently reported extrinsic factors driving both initiation and continuation of ecigarette use. Other reasons varied across intrinsic and extrinsic domains: smoking cessation was a commonly cited intrinsic motivation, often reported alongside other factors. Structural extrinsic factors such as regulatory policies appeared to be less recognized by young adults, suggesting a gap in awareness or compliance to such regulations. These findings indicate the need for further research to better understand young adults' perceptions of and interactions with regulatory measures concerning e-cigarette and tobacco use.< Réduire