INTRODUCTION: Attention deficit hyperactivity disorder (ADHD) is a 
neurobiological condition essentially characterised by inattention, 
hyperactivity and impulsiveness, and has a prevalence of around 5%. Because it 
is a biological disorder, both boys and girls with ADHD display these same 
symptoms, but more boys are diagnosed with ADHD (in a ratio of 3 to 1).
AIM: To examine the differences between the two sexes, their prevalence and 
possible female subtypes in ADHD.
PATIENTS AND METHODS: We conducted a retrospective study of 172 patients of both 
sexes who were attended as hospital neuropaediatric outpatients in the year 2004 
according to Diagnostic and statistical manual of mental disorders (DSM-IV-TR) 
criteria. Their ages ranged between 4 and 14 years and they were divided into 
three groups: under 6, between 6 and 10, and from 11 to 14 years old. The girls 
were subdivided into four subtypes, in order of greater to lesser prevalence: 
shy, hypersociable, hyperactive and changeable.
RESULTS: Both sexes showed the same response to methylphenidate. Only the group 
of boys presented other comorbidities such as negativism and conduct disorders; 
approximately 25% of them required treatment with atypical neuroleptic drugs.
CONCLUSIONS: a) Girls have certain specific clinical manifestations within the 
three common symptoms; b) methylphenidate is equally effective in both sexes; c) 
only boys display other disorders such as negativism and conduct disorders; and 
d) the brains of males and females are quite similar, but symptoms are expressed 
differently depending on environments and levels.