This is a case study of a male child, EE, aged 8+ years, who was described as rather disruptive in class during lesson. For past years, his parents, preschool and primary school teachers noted his challenging behavior and also complained that the child showed a strong dislike for mathematics and Chinese language – both are examinable academic subjects. As a result of the disturbing condition, EE was referred to an educational therapist at a private intervention center for a diagnostic assessment. The child was identified with Attention Deficit-Hyperactivity Disorder (ADHD)-Combined subtype. This aim of this paper is to discuss about the effects of ADHD on mathematics learning and how to avoid misdiagnosis or over-diagnosis of a behavioral-cum-learning disorder.