Cerebral palsy (CP) is the most prevalent physical disability in children and is often accompanied by other neurodevelopmental disorders (NDDs) such as attention deficit hyperactivity disorder (ADHD). Both conditions are influenced by genetic and environmental factors and significantly affect daily functioning. This study aims to estimate the prevalence of ADHD in school-aged children with CP from a large, population-based registry and explore associated factors including sex, material and social deprivation, epilepsy, prematurity, CP subtype, and motor functioning. This cross-sectional study linked a population-based registry (the Registre de la paralysie cérébrale du Québec [CP Registry]) and 2 administrative health claims databases (the Régie de l'assurance maladie du Québec [RAMQ] and Maintenance et Exploitation des Données pour l'Étude de la Clientèle Hospitalière). The study included children diagnosed with CP born between 1999 and 2002, tracked through these databases. ADHD diagnosis was identified using International Classification of Diseases codes and specific ADHD medication prescriptions. Odds ratios and 95% confidence intervals were used to explore factors associated with an ADHD diagnosis. The study comprised 302 children with CP and 6,040 controls matched by age, sex, and region. The prevalence of ADHD in the CP cohort was significantly higher (38%) compared with the control group (12%). Univariate analysis showed that odds of ADHD in the CP cohort were higher in male children (OR 1.63, 95% CI 1.02-2.62) and individuals with no epilepsy diagnosis (OR 1.70, 95% CI 1.02-2.87), a spastic hemiplegic CP subtype (OR 1.87, 95% CI 1.10-3.20), and less severe motor impairment (OR 2.48, 95% CI 1.37-4.65). In the multivariate analysis, odds of ADHD were only higher in those with less severe motor impairment (OR 2.02, 95% CI 1.07-3.94). ADHD is significantly more prevalent among children with CP compared with their peers, aligning with previous literature that suggests a neurodevelopmental overlap. The study highlights the importance of considering NDDs in CP management, particularly ADHD, which may contribute to the challenges faced by these children. Future research is needed to explore the neurobiological links between CP and ADHD and the impact of NDDs on health outcomes in this population.