Background Hospital-acquired pneumonia(HAP) is the most common and most serious nosocomial infection for cardiac surgery patients, with high incidence and fatality rate1. It is important for cardiac surgeons to correctly identify HAP, assess the severity, and then adjust anti-infection method, which can reduce the mortality rate, shorten hospitalization time, and reduce the waste of medical resources. The purpose of this research is to evaluate the application value of lung CT in diagnosis and treatment of HAP after cardiac surgery. Methods A retrospective analysis was conducted for clinical data about 76 cardiac surgery patients who were diagnosed with HAP during January to December 2013. The clinical data mainly included symptoms, physical signs, laboratory examinations(such as routine blood tests and serum procalcitonin), and lung CT and X-ray data. Our focus is on the comparison between lung CT and X-ray data. Results The positive diagnostic rate, false negative rate, and false positive rate of lung CT were 71 / 76(93.4%), 5 / 76(6.6%), and 1 / 76(1.3%) respectively. The coincidence rate of X-ray and CT was 45 / 76(59.2%), and the false negative rate of X-ray was 23 / 76(30.3%). Conclusion Lung CT is better than X-ray in diagnosis of HAP after cardiac surgery and assessment of severity, and has greater significance for guiding the rational use of antibiotics. Therefore, lung CT is worthy of application and popularization. Background Hospital-acquired pneumonia (HAP) is the most common and most serious nosocomial infection for cardiac surgery patients, with high incidence and fatality rate1. It is important for cardiac surgeons to correctly identify HAP, assess the severity, and then adjust anti-infection The purpose of this research is to evaluate the application value of lung CT in diagnosis and treatment of HAP after cardiac surgery. Methods A retrospective analysis was conducted for clinical data about 76 cardiac surgery patients who were diagnosed with HAP during January to December 2013. The clinical data mainly included symptoms, physical signs, laboratory examinations (such as routine blood tests and serum procalcitonin), and lung CT and X-ray data. Our focus is on the comparison between lung CT and X-ray data. Results The positive diagnostic rate, false negative rate, and false pos The coincidence rate of X-ray and CT was 45/76 (59.2%), respectively. The prevalence of lung CT was 71/76 (93.4%), 5/76 (6.6%), and 1/76 and the false negative rate of X-ray was 23/76 (30.3%). Conclusion Lung CT is better than X-ray in diagnosis of HAP after cardiac surgery and assessment of severity, and has greater significance for guiding the rational use of antibiotics Thus, lung CT is worthy of application and popularization.