Obesity is a leading cause of preventable death in America and its prevalence is increasing at an alarming rate. While it is known that individuals with specific obesity-related medical conditions perform poorly on neuropsychological tasks, recent evidence suggests that cognitive dysfunction in obese individuals may occur independently of medical co-morbidities. This study examined neuropsychological performance in a clinical sample of extremely obese patients. Individuals seeking surgical treatment of obesity (N=68) were administered cognitive tests as part of a standard pre-surgical evaluation. Results indicated significant differences in performances of extremely obese individuals on tests of executive functioning (planning, problem solving, mental flexibility) in comparison to normative data. No significant differences emerged between obese patients with and without co-morbid medical conditions of hypertension, type II diabetes, and obstructive sleep apnea on the neuropsychological tasks specific to executive functioning. Taken together, these results provide further evidence of specific cognitive dysfunction in extremely obese individuals.