Background The global outbreak of influenza A (H1N1 ) has led to the Ministry of Health of China listing it as one of the A-class infectious diseases.Pneumonia is the most serious complication of influenza A,commonly causing death.Populations are ordinarily susceptible to influenza A.This study aimed to investigate the imaging manifestation features of cdtical influenza A (H1 N1 ) pneumonia and to improve its diagnostic techniques.Methods A total of seven death cases from critical influenza A (H1 N1 ) pneumonia were retrospectively analyzed on their imaging manifestations and autopsy data.Pulmonary CT scanning was performed for five cases,with one receiving additional chest X-ray and chest CT scanning,and chest postero-anterior position X-ray examination was performed for other two.Autopsy was performed for five cases and postmortem examinations were performed for other two cases.Results The seven cases of influenza A showed critical manifestations in 4-7 days after symptoms onset,with two having basic diseases of diabetes and one being pregnant.Extensive blurry high-density shadows of bilateral lungs were found in three cases,which were most obvious in middle and infedor parts of lungs.Pulmonary CT scanning revealed bilateral flaky parenchymal shadows in peripheral,dorsal and fundus segments of the middle-inferior parts of lungs,with one case of complicated pneumothorax,atelectasis and pleural effusion and another case of thin-walled cavity and dilated bronchi shadows in the superior parts of lungs.Conclusions Diagnostic imaging is an important assessing tool for cdtical influenza A (H1N1) pneumonia The imaging manifestations are characteristic instead of being specific.The definitive diagnosis can be made in combination with clinical examinations and laboratory tests.