This research examined the emotion recognition abilities of preschoolers with and without hyperactivity and aggression. Previous research identified that school age children with Attention Deficit Hyperactivity Disorder (ADHD) have more difficulty understanding facial expressions associated with emotions, take longer than their age-matched peers to identify emotions, make more emotion recognition errors, and often misidentify sadness as anger. Previous research has also found that inattention and misidentification of emotions is significantly associated with the well-documented social disorder of children with ADHD. However, there is a lack of research focused on this inattention and misidentification of emotions in preschoolers with ADHD. To these purposes, 39 preschool boys ages 3-5 years old were recruited with 26 boys in the hyperactive and/or aggressive group (H/A) and 13 boys in the comparison group (C). Each preschooler was administered measures that assessed affect, cognitive functioning, emotion recognition from photographs, and emotion recognition from videos. The emotion recognition tasks examined a preschooler's ability to recognize happiness, anger, sadness, and surprise from two sets of photographs (i.e., salient and subtle set) and from video clips. These results showed that emotion recognition was more difficult for preschoolers with hyperactivity and/or aggression than preschoolers without hyperactivity and/or aggression with a specific deficit in the recognition of sadness. This research supported previous research, which showed that children with ADHD paid less attention to subtle emotions than their peers. This research also identified subtle sadness as the key deficit area, which suggested future research should focus on designing interventions aimed at improving recognition of sadness. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]