Attention deficit hyperactivity disorder (ADHD) is a frequent neurodevelopmental disorder characterised by both its clinical heterogeneity and co-existing comorbid disorders. The prevalence of these disorders is higher in patients with ADHD than in those without the condition and, conversely, ADHD is more prevalent in patients diagnosed with these comorbid conditions than in those without them. This can be observed, for example, with anxiety disorders, tics, reading disability, sleep disorders and enuresis. In our department at Nice Paediatric Hospitals, we have drawn attention to some such comorbid disorders; namely, enuresis, obesity and atopy. Allergy and neuropsychiatric disorders Atopy, a term derived from the Greek atopia, meaning ‘different’ or ‘out of place’, was originally proposed in 1923 to include asthma and allergic rhinitis. Eczema, or atopic dermatitis (AD), was added to the group in 1933. Its prevalence in childrem increased from 3% before 1960 to at least 16% in 2000, although this strongly varies according to local environmental conditions (air pollution, latitude, and so on). Atopic manifestations follow a typical sequence of progression, with clinical signs of AD predating the development of asthma and allergic rhinitis – a phenomenon known as the ‘atopic march’.