We examined the prevalence of inattention, hyperactivity, and impulsivity (attention-deficit hyperactivity disorder [ADHD]-like symptoms) at 7 and 18 years in a Greek birth cohort, and associated factors. Information was derived from a representative sample of 2695 Greek individuals followed-up from birth to18 years through 3 questionnaire surveys (1983, 1990, 2001). At 7 years, the prevalence of hyperactivity was 7%, inattention 9.5%, and impulsivity 7% for all children, while a significant decrease was observed at 18 years. Adverse perinatal factors, poor academic performance, fights or quarrels with peers, comorbidity, and a higher frequency of physical punishment and accidents during childhood were found to be associated with ADHD-like symptoms at 7 years. Factors identified to be related with these symptoms at 18 years included male gender, maternal stress, smoking during pregnancy, physical punishment, and psychological problems in childhood. These longitudinal findings provide significant information for health and educational planning in Greece and other countries.