A neurodevelopmental model for understanding the spectrum of developmental disabilities postulates that developmental delay, dissociation, and deviance reflect underlying central nervous system dysfunction. In this study, we determined the occurrence of the dissociated and developmentally deviant behavioral profile of attention-deficit–hyperactivity disorder (ADHD) among children with and without developmental cognitive delays (borderline-to-mild intellectual disability) in a population-based birth cohort (n=5718). Among the 70 children identified to have borderline-to-mild intellectual disability, 30% (n=21; 7 females, 14 males) met research criteria for ADHD, compared to only 6.4% of children without intellectual disability (n=358; 88 females, 270 males). The odds ratio for comorbid ADHD for children with versus without borderline-to-mild intellectual disability was 6.3 (95% confidence interval: 3.7–10.6; p<0.001). These data illustrate that developmental dissociation and/or deviance, as represented by ADHD, are more likely to occur in the context of developmental delay, represented by borderline-to-mild intellectual disability.