The comorbidity between physical and mental health conditions is challenging and frequently goes unrecognized in practice. Associations between Attention-Deficit/Hyperactivity Disorder (ADHD) and physical conditions have been reported in youth. However, prior research failed to: (1) address the patterns of associations in early childhood, middle childhood, and adolescence within the same population sample; (2) consider a large set of physical disorders at the same time; (3) take confounders into account. Our goal was to assess the associations between ADHD symptoms and a broad set of physical conditions across developmental periods. This birth cohort study (n = 2057) is the first to explore the associations between ADHD and a wide range of medical conditions by encompassing the whole early development from 5 months to 17 years in the same sample and relying on innovative network analyses. We found significant associations between ADHD symptoms and several physical conditions, some of which were observed in early childhood, middle childhood, and adolescence (e.g., asthma, sleep problems) or were confounded by socioeconomic status or psychiatric comorbidities (e.g., body mass index, dental caries). The study calls for an effective integrated care model encompassing mental and general healthcare across the developmental period.< Leer menos