This study investigated whether specific behaviors observed in 30 month-old low-birthweight children are predictive of diagnosis of attention-deficit/hyperactivity disorder (ADHD) and school difficulties at age 8. Videotapes of 571 participants were coded using the Attention-Deficit Hyperactivity Disorder Observational Rating Scale (ADHD-ORS). Logistic and discriminant analyses were conducted using the three scale factors. High scores on one factor, Inattentiveness, predicted physician diagnosis and/or school difficulties 5 1/2 years later. The Inattentiveness factor also discriminated a linear sequence of diagnostic groups, two of which were statistically significant. These findings suggest that certain behaviors can be identified before the age of 3 by trained observers and that this identification that make a future ADHD diagnosis and/or school difficulties more likely.