Parents have reported emotional regulation problems in cognitive disengagement syndrome (CDS) and attention deficit and hyperactivity disorder (ADHD). The first objective of this research was to explore the differences between the parents’ ratings on CDS, ADHD, hyperactivity/impulsivity, inattention, anxiety, depression and emotional dysregulation. The second one was to compare the predictive capacity of CDS and ADHD over anxiety, depression and emotional regulation problems. The third one was to analyze the mediation of emotional dysregulation in CDS, ADHD, hyperactivity/impulsivity, inattention, and anxiety and depression. The sampling used was non-probabilistic. The final sample consisted of 1,070 participants (484 fathers and 586 mothers) who completed the Emotion Regulation Checklist (ERC) and the Child and Adolescent Behavior Inventory (CABI). In relation to the first objective, first, mothers reported more emotional regulation problems in children than in fathers. Second, emotional regulation problems were more strongly correlated with hyperactivity/impulsivity. Significant differences were found in all father scores, except for anxiety and the emotional regulation subscale. Regarding mothers, significant differences were only observed in ADHD scores, hyperactivity/impulsivity, and depression. Both parents reported more problems in older children, except for hyperactivity/impulsivity scores and ADHD rated by mothers. According to the second objective, CDS scores were found to significantly predict anxiety and depression scores, but not those of inattention or emotional regulation problems. Finally, in relation to the third objective, emotional regulation problems mediated the relationships between CDS, ADHD, and anxiety and depression. In conclusion, the data support the importance of emotional regulation problems in understanding CDS and its relationship with ADHD, anxiety, and depression.