Objectives: Little is known about the distribution and intergenerational transmission of attachment representations in ADHD populations and further how attachment may influence the prognosis of ADHD. In this study we aimed to investigate attachment distribution, intergenerational transmission and the potential impact of maternal and child attachment representations on treatment response in a sample of children with ADHD. Methods: Sixty mother-child dyads from families with offspring ADHD were recruited. Attachment representations were assessed with the Adult Attachment Interview (AAI) and the Child Attachment Interview (CAI). ADHD symptom severity was assessed at four time points with the ADHD-Rating Scale. Results: Of the children, only 15% and among the mothers, only 23% were securely attached. Contrary to predictions, the association between maternal and child attachment representations (Secure versus Insecure) did not reach statistical significance as we found overall concordance rate to be 63% (kappa = −0.05). Neither child nor maternal attachment significantly predicted treatment response. Conclusions: In families with offspring ADHD, the prevalence of insecure attachment was remarkably high in the children as well as in the mothers. Intergenerational transmission of attachment was very low and in short-term follow up, attachment representations did not affect treatment outcome. Our findings support previous research in suggesting that the relationship between ADHD and Insecure attachment is complex. Nevertheless, the importance of considering attachment as a factor in the treatment, functional impairment and long term prognosis of children with ADHD remains.