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.