Source of initial access to disability services, accommodations received as supports on campus, and the rate of continuous enrollment data was measured and compared for students diagnosed with ADHD prior to age eighteen and those diagnosed with ADHD after age eighteen. These two groups were compared to analyze the assumption that students who were already immersed in a special services environment would be more capable of accessing services in the postsecondary setting more readily than those who had been newly diagnosed just prior to or after entering postsecondary education. Students with a diagnosis prior to age eighteen (n = 34) and those with a diagnosis after age eighteen (n = 29) comprised a naturally formed group of university students attending the university from August of 2011 through May of 2012. As reflected in the subject results, the source of referral to the disability service providers by those diagnosed prior to age eighteen was not significantly different from those students diagnosed after age eighteen. As reflected in the accommodations requested and approved, those diagnosed prior to age eighteen did not show significant differences in requests from those diagnosed after age eighteen. As reflected in the rate of continuous enrollment from freshman through senior year, the students diagnosed prior to age eighteen were not significantly different from those students who were diagnosed after age eighteen. The study's results should encourage further research in both secondary and postsecondary institutions. Secondary settings can use the results of this study to examine their current level of transition services for students with disabilities to ascertain if the services they provide lead toward successful transition to postsecondary education. Postsecondary institutions can use the results of this study to examine how to increase accessibility to those students on campus with disabilities, enhance services and accommodations that allow students with disabilities to be successful, and develop linkages with secondary schools to make them aware of appropriate supports at the postsecondary level and how the faculty can use appropriate goals at the secondary level to prepare their students with disabilities for postsecondary education, if that is their intended transitional path. [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/en-US/products/dissertations/individuals.shtml.]