Several theories attempt to explain the high co-occurrence of Attention Deficit/ Hyperactivity Disorder (AD/HD) and Conduct Problems (CP). A strong possibility is that AD/HD behaviours lead to the development of CP, due to family coercive interaction patterns, maintained through parental false beliefs regarding child problem behaviour. We compared maternal perceptions about AD/HD behaviors and CP, and the possible reactions elicited by such behaviours. The sample consisted of 317 mothers of boys and girls aged 4–6. Four versions of The Parental Account of the Causes of Childhood Problems Questionnaire were used, in which a vignette was ascribed to either a boy or a girl displaying some of the major AD/HD behaviours or CP. The results showed that CP were perceived as significantly more severe than AD/HD behaviours. Moreover, AD/HD behaviours were attributed to biological causes more often than CP, and less strict rearing practices were chosen for AD/HD symptoms. Our findings provide evidence that mothers usually perceive AD/HD behaviours and CP as separate entities and may behave accordingly with their children.