Introduction. There are few studies about preschool attention deficit hyperactivity disorder (ADHD) prevalence. Aim. To study the prevalence of ADHD in preschoolers using an specific scale (ADHD-RS-IV-P-Es) developed for this age range. Subjects and methods. We evaluated the prevalence of possible ADHD in a representative sample of preschoolers in Navarra and La Rioja, Spain. Results. We find a range of prevalence between 2.5-4.1% depending on the criteria that was used (more or less strict). Conclusions. There are specific tools that can be use in preschool ADHD study. The prevalence of preschool ADHD in Spain is similar than in other countries. The frequency of symptoms in this age range is similar to the found in school age children.