Attention-Deficit/Hyperactivity Disorder (ADHD) is associated with academic failure in high school; however the underpinnings of these difficulties are insufficiently understood. This study examined deficits in self-regulated learning in a sample of high school students with ADHD (n=32) compared to demographically similar classmates without ADHD (n=18). A multimethod battery of self and parent rating scales and cognitive tasks measured aspects of intrinsic motivation, extrinsic motivation, and goal-directed executive functions. A multiple regression modeled predictors of current Grade Point Average (GPA). Results indicated that high school students with ADHD placed lower value on academics (d = 0.99), were less likely to use goalsetting strategies (d = 0.95), possessed lower levels of metacognition (d = 1.86), and showed significant deficits in task-based cognitive flexibility (d = 0.80). After controlling for covariates, the set of self-regulated learning variables explained 23% of the variance in GPA, with metacognition (6% of variance explained) and cognitive flexibility (7% of variance explained) serving as significant predictors of outcome. Findings suggest that higher-order executive function deficits play a critical role in the academic functioning of high school students and students with ADHD show large deficits in these areas. Thus, interventions that target metacognition and cognitive flexibility (i.e., the ability to think through decisions before acting, inhibit automatic responses, and make effective decisions for a desired goal) may be particularly promising to remediate ADHD-related academic problems in high school. [This paper was published in "Journal of School Psychology" v77 p67-76 2019.]