The aim of this study was to investigate whether dysfunctions could be seen in the brainstem of adults with attention-deficit/hyperactivity disorder and if these could be associated with specific brain structures. Further, the purpose was to study the connection between proposed dysfunctions in the brainstem and self-rated symptoms. The study included 15 people with an AD/HD diagnosis and a control group of 15 people without any known diagnosis. Each group consisted of 7 men and 8 women. Methods used were a complex auditory brainstem response called SensoDetect-Brainstem Evoked Response Audiometry (SD-BERA) and the symptom scale Adult ADHD Self-Report Scale (ASRS). The results indicated that it is possible to identify people with AD/HD using SD-BERA with a sensitivity of 86,67% and a specificity of 93,33%. Furthermore, a significant correlation was found between SD-BERA and ASRS, Spearman’s rs = 0,582. Dysfunctions in the brainstem were mainly connected to the area around inferior colliculus and partly to pons and thalamus. SD-BERA showed a significantly higher activity within the AD/HD group compared to the control group. These results point to the value of using auditory brainstem response as a complementary method in diagnosing AD/HD.