Objective: Aspergers Syndrome can present as comorbid with attention-deficit/hyperactivity disorder (ADHD). Very few cases of the assessment and treatment of this comorbidity in adulthood are described in the research literature. Method: A 26-year-old patient as suffering from ADHD in combination with Aspergers Syndrome is diagnosed. Treatment is started with methylphenidate (MPH), and the patient's clinical response is observed, psychological tests concerning attention are analyzed, and a functional magnetic resonance imaging (fMRI) examination is performed during an attention-task. Results: On the functional magnetic resonance imaging, a reduction of cerebral activity bilaterally in the parietal lobe under the influence of MPH is detected. Conclusion: Besides the neurophysiological findings, this case reports the complex impairment caused by the combination of AD/HD with Aspergers Syndrome and the broad social and behavioral benefits of treatment with MPH for this comorbidity. (Contains 2 figures and 1 note.)