In this retrospective study, we evaluated the respiratory capacity of 44 patients admitted to the Unit of Infectious Diseases (UID) of our hospital from 10 th August 2009 to 15 th November 2010. These were followed with Forced Vital Capacity (FVC), Forced Expiratory Volume in 1 sec (FEV1) and Carbon Monoxide Diffusing Capacity (DLCO) for a period of six months after their discharge. The rationale for the study was published data that H1N1 presents with hypoxemia and acute respiratory distress syndrome (ARDS) [14] [15] [16] [17] 28, 29] . In addition, we examined the clinical characteristics of these patients.