Attention Deficit/Hyperactivity Disorder (ADHD), formerly regarded as a typical childhood disorder, is now known as a developmental disorder persisting over the lifespan. Starting in preschool-age, symptoms vary depending on the age group affected.According to the variability of ADHD-symptoms and the heterogeneity of comorbid psychiatric disorders, a broad review of recent studies was performed. These findings were summarized in a developmental psychopathological model, documenting relevant facts on a timeline.Based on a genetic disposition and a neuropsychological deregulation, there is evidence for factors which persist across the lifespan, change age-dependently, or show validity in a specific developmental phase. Qualitative changes can be found for children in preschool-age and adults.These differences have implications for clinical practice as they can be used for prevention, diagnostic proceedings, and therapeutic intervention as well as for planning future studies. The present article is a translated and modified version of the German article "Entwicklungspsychopathologie der ADHS", published in Zeitschrift für Psychiatrie, Psychologie und Psychotherapie, 56, 2008, S. 265-274.