Very little research exists on how self-perceived emerging adult status is associated with substance use among low-income emerging adults. The Inventory of Dimensions of Emerging Adulthood (IDEA) was administered to emerging adults (EAs) ages 18-25 screened for substance use problems (n = l05) in a state-subsidized, not-for-profit treatment agency. We examined whether the defining dimensions of Arnett's (2000a) emerging adulthood theory were associated with substance use frequency and substance-related problems, including: identity exploration, self-focus, possibilities, optimism, negativity/instability, and feeling in-between. In multivariate models, feeling in-between was positively associated with substance-related problems. An interaction term between minority status and feeling in-between approached statistical significance (p = .057). Further, IDEA scale score means were comparable to those found in college student samples. Implications for theory revision are discussed.