Objective: To evaluate the psychological impact of receiving a diagnosis of ADHD in adulthood and treatment with medication and to examine how diagnosis and treatment with medication changes an individual's self-perception and view of the future. Method: Participants were eight individuals diagnosed with ADHD at a tertiary service. Semistructured interviews were conducted and the data were analyzed according to the principles of Interpretative Phenomenological Analysis. Results: Three master themes emerge from the analysis: Participants engage in a (a) review of the past, particularly how they feel different from others, (b) the emotional impact of the diagnosis, and (c) consideration of the future. These themes suggest a six-stage model of psychological acceptance of a diagnosis of ADHD: (a) relief and elation, (b) confusion and emotional turmoil, (c) anger, (d) sadness and grief, (e) anxiety, and (f) accommodation and acceptance. Conclusion: The model indicates an important role for psychological treatment, which should begin at the point of diagnosis. Cognitive behavioral techniques will help clients diagnosed with ADHD in adulthood cope with the adjustment process. Adults should be taught skills to anticipate future hurdles and challenges and apply appropriate coping strategies.