Working memory (WM) is often a deficit in children with attention deficit hyperactivity disorder (ADHD) and is related to other impairments within this clinical population. Cogmed, a computerized WM training program, is sometimes prescribed as a treatment for ADHD youth - although the efficacy of this intervention remains controversial. Our main objective was to explore whether ADHD youths' motivational style predicted training engagement or performance on outcome measures. A second objective was to obtain a more nuanced understanding of potential benefits of the program via interviews.The current study focuses on 10 ADHD youth (age 8 - 14 years) randomized to a modified 30-session Cogmed protocol, as part of a larger clinical trial. Youth completed an adapted Self-Regulation Questionnaire (SRQ) and participated in a semi-structured interview at three-month follow-up.All youth showed adherence to the modified Cogmed protocol. More externally motivated youth started training at a higher level of performance and also reached higher peak performance. At follow-up, higher levels of external forms of motivation correlated with better spatial working memory but worse academic performance. In addition, greater endorsement of external motivation was associated with lower self-concept. Qualitative analyses suggested that youth displayed multiple motivational styles with regard to participation and noted subjective improvements in their everyday lives.Youth endorsed both extrinsic and intrinsic motivation and reported that training was useful. Larger studies should consider assessing individual differences in motivational style and incorporating qualitative methodology to identify additional intervention outcome variables to consider amongst ADHD youth.