This is a 3-year project. Our previous studies have collected blood samples and spatial working memory data of 382 patients with ADHD and 150 healthy subjects. In this 3-year project, we will recruit 232 healthy subjects, aged 7-18 years. The measures include (1) interviews for psychopathology (K-SADS-E), (2) questionnaires to measures ADHD symptoms (SNAP-IV), and (3) neuropsychological tests: Spatial Working Memory task of the CANTAB. In the first year, a case-only GWAS on spatial working memory (n = 254) will be conducted. In the second year, a control-only GWAS on spatial working memory (n = 254) will be conducted. In the third year, findings from the initial two GWAS will be replicated in a validation sample composed of 128 patients with ADHD and 128 healthy controls.