Males with Attention Deficit/Hyperactivity Disorder (AD/HD) are referred to specialists significantly more frequently than females. The aim of this study was to examine differences in mothers’ and prospective educators’ self-efficacy beliefs and severity perceptions towards boys and girls with AD/HD and to explore the inter-relationships between those perceptions and referral judgements. One hundred and fifteen female prospective preschool educators and 118 mothers of boys and girls aged 4-6, enrolled in kindergartens in Athens completed a questionnaire that: (a) presented a vignette describing a typical boy or girl with AD/HD, and (b) was followed by two scales exploring severity perceptions and self-efficacy beliefs with reference to the child described in the vignette. Mothers’ sense of self-efficacy was higher than educators’ and both samples had higher sense of self-efficacy towards girls with AD/HD than boys. Educators rated the boys’ behaviour as significantly more severe than girls’. Finally, perceived self-efficacy predicted severity perceptions and severity perceptions predicted referral decisions. To conclude, adults’ differentiated perceptions of severity of AD/HD in boys and girls, which might be influenced by their own limited self-efficacy beliefs, especially towards males, might account for a proportion of the differences in referral ratio of boys and girls with AD/HD.