Most cases of ADHD occur in children under five, and this situation calls for screening tools with high sensitivity and specificity for early age. This study presents the ADHD-3P, a new screening tool developed with Spanish population for preschool children. From an initial pool of 151 items, face validity analyses, followed by item analyses and analysis of the scale, were carried out. A 27-item scale (? = .95) composed of three factors: hyperactivity (? = .92), inattention (? = .92), and other symptoms (? = .81) resulted from the analyses. Discriminant power was high (89.7% for ADHD, and 88.3% for non-ADHD). Diagnostic performance was evaluated through Receiver-Operating Characteristic curves, and excellent sensitivity (92.86%) and specificity (89.86%) were obtained. In sum, the ADHD-3Pis a promising tool to be used by parents, teachers, and pediatricians.