Ahe adult patients with attention deficit hyperactivity disorder (ADHD) are characterized by an increased vulnerability to daily life stressors. Cortisol awakening response (CAR) can be used as an index of the adrenocortical activity that relates to chronic stress. Although gender differences in cortisol response have been explored in children with ADHD, there is a lack of gender studies in adults with this disorder. The aim of the present study is to evaluate possible gender differences in CAR in adults with ADHD. A total of 50 patients (22 female, age 37.00±8.62 years, and 28 male, age 33.86±9.57 years), with ADHD were recruited from the program for adults with ADHD in the Department of Psychiatry of the Hospital Universitari Vall d’Hebron. Patients fulfilled current DSM-IV diagnostic criteria for ADHD. Psychiatric and organic comorbid disorders were excluded and all the patients were naïve to psychostimulant treatment. Four salivary cortisol samples were collected at 0, 30, 45 and 60 minutes after awakening (work days). Mean increase in CAR was 10.39±8.68 nmols/l for men and 10.29±9.13 nmols/l for women. T-test comparisons showed no significant gender differences in CAR in adults with ADHD (t= 0.033, z=0.974). As reported in children, adults with ADHD show no differences in CAR. Albeit these results are still preliminary, they suggest some gender differences in CAR between adults with ADHD and cortisol response in general population.