Attention Deficit Hyperactivity Disorder (ADHD), a common neurobehavioral disorder in childhood, negatively impacts academic and social functioning, both of which later influence adulthood (Bose, 2013). This action research study focuses on comparing the prevalence of on-task and off-task behaviors exhibited by elementary age students diagnosed with ADHD in a traditional classroom structure versus a Montessori classroom structure. While much time and research has been conducted to assist educators in meeting the needs of students with learning disabilities through interventions, less research has focused on non-conventional educational environments as an alternative for children with ADHD. In this study, on-task and off-task behaviors of second and third grade elementary students (with parent-reported ADHD diagnoses) will be examined during core instruction in a school district that offers parents a choice between traditional instruction or Montessori instruction. A mixed methods approach using a structured observation system, field notes, narrative observations, teacher interviews, and parent questionnaires will be used to collect qualitative and quantitative data. While further studies will be beneficial to determine to what degree, if any, a difference in classroom behavior is present in students with ADHD between these two contrasting classroom structures, this action research study will serve to benefit parents and educators in understanding the possible effects of on-task and off-task behaviors to academic achievement in the two different instructional environments. [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.]