Background: The aim of this investigation was to examine the construct validity and distinctiveness of the inattentive type (IT) and combined type (CT) of Attention-Deficit/Hyperactivity Disorder (ADHD) in a Latino/Hispanic sample. Method: A comprehensive assessment was conducted with a clinically diagnosed school-based sample of 98 children aged 6 to 11 (CT = 44; IT = 25; control group = 29). Results: Both ADHD groups were impaired on academic achievement measures, presented more ADHD-type behaviors during math and vigilance tasks, and exhibited greater internalizing symptoms. The IT group had a later onset of inattention symptoms, presented more sluggish cognitive tempo symptoms, was less prone to initiate social interactions or to be assertive and more self-controlled in social interchanges, was less likely to have externalizing behaviors, had mothers who reported less child-related family stress, and was less impaired in their adaptive functioning. Conclusions: Findings supported the construct validity of ADHD in this culturally different sample and suggested that the CT and IT represent distinct disorders.