We describe 3 critically ill patients with pneumonia complicated by lung abscesses and contralateral pneumonia due to spill of purulent secretions into the healthy lung. Although the clinical picture of lung abscess often runs an indolent course, this was not observed in these critically ill patients, who all died from this complication. Diagnosis was delayed as chest X-ray underestimated lung pathology compared to computed tomography (CT) scan. Therefore percutaneous chest tube drainage and placement of a double-lumen endobronchial tube to protect the healthy lung were delayed and spill of purulent secretions into the contralateral lung occurred. These cases show the importance of rapid evaluation by CT scan of the chest in mechanically ventilated patients with slowly resolving infiltrates on chest X-ray.