Data on the genetic and environmental factors underlying the co-occurrence of Cognitive Disengagement Syndrome (CDS), Attention Deficit Hyperactivity Disorder (ADHD), and Emotional Dysregulation (ED) are limited. This study aimed to explore the nature of the associations between CDS, ADHD with ED, and to assess the role of shared etiological factors in explaining their comorbidity. We analyzed a sample of 400 Italian twin pairs aged 8-18, from Northern Italy and enrolled in the Italian Twin Registry. Bivariate genetic analyses were conducted using parent-rated CBCL scores for CDS, ADHD, and ED. For both CDS-ED and ADHD-ED associations, the best-fitting models were Cholesky AE models (-2LL = -849.167 and -339.030, respectively; > 0.05), suggesting that the covariation was mainly due to additive genetic factors (CDS-ED-A = 0.81, 95% CI [0.66-0.95]; ADHD-ED-A = 0.86, 95% CI [0.75-0.95]). More than half of the genes were shown to be shared among the phenotypes. Non-shared environmental contributions were smaller (CDS-ED-E = 0.19, 95% CI [0.05-0.34]; ADHD-ED-E = 0.14, 95% CI [0.05-0.25]), indicating interrelated but distinct constructs. Despite some limitations, particularly the exclusive use of the CBCL, findings highlight the importance of monitoring ED symptoms in individuals with CDS or ADHD, and vice versa.