Impaired decision making and Working Memory (WM) are among the characteristic symptoms of patients affected by Attention Deficit/Hyperactivity Disorder (ADHD). In order to investigate whether a WM training can affect the attitude towards risky decision making, we designed a study where participants had to perform a Probabilistic Gambling Task. Our study has demonstrated that WM training affects in a different way controls and ADHD patients, who showed an increased tendency towards a risk-taking attitude in case of the adaptive variant of the memory task. In ADHD patients, the frontal sites appeared the most affected, whereas global brain activity was likely to be affected in controls. This study shows also the benefits of cognitive training in ADHD patients, but in healthy subjects too.