Many students with attention-deficit/hyperactivity disorder (ADHD) exhibit deficits in motivation to pursue long-term goals. Students with ADHD have particular difficulty with motivation to complete homework-related tasks and often fail to complete assignments. Although these problems are common and may impact academic performance, no homework-motivation measures have been validated for use with students with ADHD. The primary goal of the present study was to evaluate the factor structure and predictive validity of a homework-motivation measure based upon the expectancy--value theory of achievement motivation. A sample of 285 middle school students with ADHD completed the measure, and confirmatory factor analysis was used to evaluate the proposed factor structure and associations with parent and teacher ratings of homework performance. A 2-factor structure emerged, and model fit was excellent. Further, student-rated ability--expectancy beliefs demonstrated significant associations with parent-rated homework problems and performance and with teacher-rated homework performance and percentage of assignments turned in above and beyond ADHD symptoms. Future directions for studying the importance of motivation in students with ADHD are provided, with particular attention to the role that reward sensitivity may play in motivation.