Background: Attention deficit hyperactivity disorder (ADHD) is the main motive for consultation at the Hospital Psiquiátrico Infantil. Materials and methods: Prospective study analyzing patients with ADHD for 2 months. Results: Recruited 555 patients, average age 8.7 (± 1.66) years, 485 (87.4%) males and 70 (12.6%) females. The most frequent subtype was combined in 440 (79.3%). We observed high comorbidity (68.1%), with externalizing disorders 143 (25.8%) patients and internalizing disorders 136 (24.5%). Epilepsy was found in eight patients. The most commonly used medications were methylphenidate for 485 cases (87.4%), followed by risperidone 45 (8.1%), fluoxetine 32 (5.8%), and without drug treatment 31 (5.6%). Mood stabilizers in 102 patients (18.4%), 32% received more than one drug. The most frequent combinations were methylphenidate with valproate, methylphenidate with risperidone, and methylphenidate with fluoxetine. Conclusions: Males attend more frequently, and the most frequent subtype is combined. Comorbidity presented in almost 70%, most predominantly with the oppositional defiant disorder. Methylphenidate is the most commonly used drug in monotherapy or in combination.