Multifactorial research must examine if disorganized attachment is specifically associated with either ODD- or ADHD-symptoms,and the mechanisms through which disorganization may become associated with externalizing problems. The present short-term longitudinal study therefore examined attachment representations, and several competences important for socio-emotional functioning, in relation to ODD- and ADHD-symptoms at T1 (N = 105, M age = 80 months) and T2 (N = 80, M age = 104 months). There was a main effect of disorganized attachment on ODD-symptoms at both time points but not on ADHD-symptoms. Disorganized children also showed lowered attention to facial expressions, a diminished ability to discriminate facial expressions, and elevated emotional reactivity. Emotional reactivity mediated the link between disorganization and ODD-symptoms at T1, but not at T2. The findings support disorganized attachment as a risk-factor for ODD-symptoms rather than ADHD-symptoms, and suggest that disorganization may become associated with ODD-symptoms through broad effects on multiple competences.