Objective: The article discusses the ADHD Observational Research in Europe (ADORE) study that examined the impact of early treatment choices on outcome within the first few months, in previously untreated children with impairing inattention, impulsivity, and hyperactivity. Methods: Data are collected from a longitudinal, observational study conducted in 10 European countries that involve 1,478 children (aged 6 to 18 years) with symptoms of hyperactivity, impulsivity, or inattentiveness. Linear model with a propensity score adjustment compares the decrease in ADHD-RS scores between baseline and last recorded visit across treatment groups (2 to 5 months). Results: At baseline, 49.9% of participants are prescribed pharmacotherapy and 44.3% a psychosocial intervention. Analysis of the effect of treatment on the evolution of ADHD-RS scores shows a positive effect of medications and either an insignificant or negative effect of psychosocial intervention. Conclusions: Early use of medication effectively reduces ADHD symptoms in routine clinical practice in Europe. The effect of psychosocial intervention has to be interpreted cautiously because the number, length, and level of standard of the sessions are not taken into account in the analyses. (Contains 2 tables and 2 figures.)