An increasing number of studies are finding a relationship between obesity and Attention-deficit/Hyperactivity Disorder (ADHD), although little is known about the potential mechanisms underlying this relationship. The present study examines this potential relationship and possible underlying mechanisms of maladaptive eating patterns and impulsivity trait characteristics in a longitudinal analysis of a college-student sample (n = 264). Body fat percentage (BF%) was collected at two time points during the student’s first semester at college and eating behavior patterns and ADHD symptomology was assessed by self-report measures. Impulsivity trait characteristics were assessed by both self-report and experimental methods. No significant relationship was found between ADHD symptoms and BF% and the change in BF% across time-points was not significantly related to any other variables studied. Relationships between ADHD symptoms, eating behavior patterns, impulsivity, and BF% were inconsistent. Findings do not support a relationship between obesity and ADHD in a non-clinical population, but highlight the complexity of underlying mechanisms of both these conditions. Implications of utilizing a college-student population and suggestions for future research are discussed.