Introduction: There is a frequent comorbidity of amphetamine-type stimulants (ATS) use disorders and attention-deficit/hyperactivity disorder (ADHD). The assumption that this patient group “self-medicate” suggests that there are different use motives for ATS addicted patients with and without ADHD. Objective: Our study investigates these potential differences in use motives. Methods: Within a mixed-method approach, we examined the use motives of adults with ATS use disorder with and without ADHD in the first and latest month of their use. For this purpose, we used the 12-item Amphetamine-Type Stimulants Motive Questionnaire (AMQ) and a mind mapping technique after verifying that these tools are applicable to adults with ADHD. Results: The mixed-method approach showed that enhancement motives were the most important motives in the first month of use (e.g., fun/kick/rush/desire, and curiosity/interest in the drug/appeal), and over time, the incidence of coping motives increased (e.g., repression and freeing the mind/not having to think/switching off). There were no differences between adults with and without ADHD in the AMQ data, while the qualitative data showed that adults with ADHD used ATS less often out of social motives. In particular, the results showed no differences in the coping dimension and, thus, did not suggest that self-medication is an important factor for patients with ADHD. Conclusions: Patients with and without ADHD show very similar motive patterns for ATS use. This indicates that ATS treatment programs addressing use motives do not necessarily have to be different for patients with and without ADHD.