the neuropsychiatric phenotype in DMD. We recruited 98 DMD boys (70 in GOSH-UK and 28 in Italy), who underwent standardised neuropsychological assessments including: WISC-IV, 3Di, Conners-3 Questionnaires, and CBCL. We report that 75% of children with ASD also meet criteria for ADHD; of the DMD boys with ASD 53% had externalising behavioural problems. Half of the boys with ADHD also met criteria for ASD, externalising and internalising behavioural problems. There was a significant coexistence of psychiatric comorbidities in boys with mutations disrupting the shorter C-terminus dystrophin isoforms (Dp260, Dp140, Dp116, Dp71) when compared with mutations at the 50 end of the gene (p = 0.02). We demonstrated that neurodevelopmental disorders are highly prevalent in DMD. Boys with mutations downstream of exon 30 are at a higher risk of suffering from coexistence of neuropsychiatric symptoms, more commonly than what observed in the general psychiatric population. These findings suggest that DMD may have a distinctive neurodevelopmental profile, requiring targeted support.