BACKGROUND: Posttraumatic stress disorder is associated with impairments in sustained attention, a fundamental cognitive process important for a variety of social and occupational tasks. To date, however, the precise nature of these impairments and the posttraumatic stress disorder symptoms associated with them have not been well understood. METHODS: Using a well-characterized sample of returning United States military OEF/OIF/OND Veterans who varied in posttraumatic stress disorder symptoms, we employed a validated sustained attention paradigm designed to probe fluctuations across two attentional states characterized by prior research, including a peak state termed "in the zone" and a less efficient, more error-prone state termed "out of the zone." Rewarded and nonrewarded conditions were employed to examine whether motivating strong task performance could ameliorate sustained attention deficits. Analyses examined associations between attentional state, availability of reward, and posttraumatic stress disorder symptoms. RESULTS: Results indicated that, consistent with prior findings, higher levels of posttraumatic stress disorder symptoms were broadly associated with impaired task performance. This impairment was driven largely by performance deficits during individuals' optimal ("in the zone") attentional state, and follow-up analyses indicated that the performance deficit was primarily associated with anhedonia and emotional numbing symptoms. However, the deficit was partially ameliorated when better performance was rewarded. CONCLUSION: Our results provide a more complex understanding of the sustained attention deficits associated with posttraumatic stress disorder and suggest that external incentives may help to enhance sustained attention performance for affected individuals.