Background: The aim of the present study was to evaluate whether findings on initial chest computed tomography (CT) of influenza pneumonia can help predict clinical outcome. Methods: We reviewed all adult patients admitted to the Emergency Department (ED) with a confirmed diagnosis of novel influenza A H1N1 virus (2009 H1N1) pneumonia, who underwent chest CT upon admission between Aug 26, 2009 and Jan 31, 2010. Radiologic findings were characterized by type and pattern of opacities and zonal distribution. Clinical outcome measures were intensive care unit (ICU) admission, mechanical ventilation, and inhospital death. Results: Of 59 patients diagnosed with 2009 H1N1 pneumonia, 41 (69.5%) underwent chest CT on admission into ED. Nine (22%) of these patients developed adverse clinical outcomes requiring the following treatments: 9 (22.0%) ICU admissions, 5 (12.2%) mechanical ventilation, and 3 (7.3%) inhospital deaths. Counting the number of patients with more than 4 involved lobes, the sensitivity, specificity, positive predictive value, and negative predictive value for detection of adverse clinical outcome were 67%, 84%, 55% and 80%, respectively. Conclusion: Extensive involvement of both lungs (over 4 lobes) is related to ICU admission, mechanical ventilation, and inhospital death. Initial chest CT may help predict an adverse clinical outcome of patients with 2009 H1N1 influenza pneumonia.