F-18 FDG PET/CT has become a useful technique in the evaluation of pulmonary lesions. We present a case of markedly increased and diffuse pulmonary F-18 FDG activity in a patient with acute respiratory distress syndrome (ARDS). High rates of glucose utilization by the inflammatory cells involved in the pathogenesis of ARDS might explain the increased pulmonary F-18 FDG uptake we observed. In the proper clinical setting, ARDS should be considered in the differential diagnosis of patients with diffusely increased F-18 FDG activity in the lungs.