Introduction <p>Sleep disorders are common yet often underdiagnosed in children with attention deficit/hyperactivity disorder (ADHD). These disturbances can exacerbate ADHD symptoms and negatively affect cognitive, emotional, and behavioral functioning. This study aimed to describe the prevalence of obstructive sleep apnea (OSA) and other sleep disorders in children with ADHD using standardized diagnostic criteria and to identify associated clinical and behavioral factors.</p> Methods <p>A cross-sectional study was conducted on 629 children aged 6–12&#xa0;years (mean age: 7.8 ± 1.5&#xa0;years) who were diagnosed with ADHD. Sleep disturbances were assessed using the Children’s Sleep Habits Questionnaire (CSHQ), the Pediatric Sleep Questionnaire (PSQ), and respiratory polygraphy. Sleep disorders were classified on the basis of the International Classification of Sleep Disorders, Third Edition (ICSD-3). Multivariate logistic regression was used to identify associated risk factors.</p> Results <p>Sleep disorders were diagnosed in 70.0% of children with ADHD. The most common disorders were insomnia (40.2%), OSA (23.4%), parasomnias (27.8%), restless legs syndrome (10.5%), and delayed sleep–wake phase disorder (4.8%). The inattentive ADHD subtype, psychiatric comorbidities, tonsil and adenoid hypertrophy, iron-deficiency anemia, and sleep-related behaviors in children with ADHD were significantly associated with sleep disturbances.</p> Conclusions <p>Sleep disorders are highly prevalent and diverse in children with ADHD. Early identification and targeted management of sleep disturbances, particularly OSA and insomnia, are essential to improving sleep quality and optimizing ADHD outcomes. Routine sleep screening should be integrated into clinical ADHD evaluations.</p> <p>Graphical abstract available for this article.</p> Graphical Abstract <p></p>