Specific learning difficulties (SLD) are reported in 8-10% of the general population. They are often associated with Attention Deficit Disorder with or without Hyperactivity (ADD/ADHD) (33-70%). These neurodevelopmental disorders are generally associated with various co-morbidities such as anxiety and depressive disorders. Previous studies, based on questionnaires, have shown more sleep disorders in this population compared with control children, particularly in children with both pathologies. The aim of this study was to evaluate sleep characteristics in Dys children with or without ADHD associated with sleep complaints. One hundred and seventeen children (49 girls) were included in this retrospective study, median age 11.2 years (range 5.2 to 18.2 years). The patients were divided into 3 categories according to their disorder: Dys (n = 62), ADD/ADHD (n = 11) and Dys-ADHD (n = 44). For each patient, the medical history, sleep disorders, Epworth sleepiness score and polysomnographic results were collected. Non-parametric comparisons were made between our groups (Kruskal Wallis, Wilcoxon and Chi²). Children with ADD/ADHD had a higher frequency of Multi-Dys disorder (65.9% compared with 38.7% without ADD/ADHD). Children with ADD/ADHD had a higher frequency of respiratory and mood disorders. At polysomnography, the main sleep disorders observed were respiratory problems, generally mild OSAS and SHRVAS (80%), sleep fragmentation (pathological EMI, 52%), and a higher percentage of L1 for our groups with Dys. Comparisons revealed differences based on psychostimulant treatment, with lower levels of sleepiness and an increase in insomnia associated with treatment. This study highlights a significant proportion of co-morbidities in Dys children with a possible impact on sleep. There were frequent complaints of sleepiness and insomnia, with a difference in the type of complaint depending on whether or not stimulant treatment was used. These results underline the importance of taking into account associated comorbidities in children with Dys with or without ADHD.