Over the past few years, an increasing number of studies have shown that playing action video games can have positive effects on tasks that involve attention and visuo-spatial cognition (e.g., visual search, enumeration tasks, tracking multiple objects). Although playing action video games can improve several cognitive functions, the intensive interaction with the exciting, challenging, intrinsically stimulating and perceptually appealing game environments may adversely affect other functions, including the ability to maintain attention when the level of stimulation is not as intense. This study investigated whether a relationship existed between action video gaming and sustained attention performance in a sample of 45 Italian teenagers. After completing a questionnaire about their video game habits, participants were divided into Action Video Game Player (AVGP) and Non-Action Video Game Player (NAVGP) groups and underwent cognitive tests. The results confirm previous findings of studies of AVGPs as they had significantly enhanced performance for instantly enumerating a set of items. Nevertheless, we found that the drop in performance over time, typical of a sustained attention task, was significantly greater in the AVGP compared with the NAVGP group. This result is consistent with our hypothesis and demonstrates a negative effect of playing action video games.