Using an experience sampling methodology, the everyday lives of 153 adolescents with low, middle, or high levels of attention-deficit/hyperactivity disorder (ADHD) characteristics as assessed by either parent or teen were examined. Twice each hour, across two 4-day recording intervals, participants in a longitudinal study of stress and health risks logged their behaviors, moods, and social contexts. Those with high, in contrast to low, ADHD symptom levels recorded more negative and fewer positive moods, lower alertness, more entertaining activities relative to achievement-oriented pursuits, more time with friends and less time with family, and more tobacco and alcohol use. Fewer associations emerged with parent-defined than with teen-defined subgroups, although the differences in alertness, peer and family contexts, entertainment versus achievement activities, and substance use were consistent across sources. Even at subclinical levels, ADHD characteristics were associated with behavioral patterns and contexts that may promote peer deviancy training, unhealthy lifestyle behaviors, and vulnerability to nicotine dependence.