We described a retrospective cohort study of 44 patients who were hospitalized with the pandemic 2009/10 Influenza A (H1N1) in the University Hospital of Alexandroupolis, Thrace from 10 th August 2009 to 15 th November 2010. So far, there has been no evaluation of H1N1 respiratory function. The correlation between the mechanisms and the impact that viruses have on the respiratory system has been established in previous published studies [14] [15] [16] [17] 28, 29, [39] [40] [41] [42] [43] [44] . As might be anticipated, we found a major decreased respiratory capacity (FEV1 -10.205, FVC -9.909, DLCO -12.409) between the measurements taken upon discharge and in the sixmonth follow-up. This occurred due to the inflammatory effects of the virus through the respiratory tract. The differentiation of respiratory capacity also varied between the measurements taken upon discharge and the three-month follow-up, but it was observed that the variation was smaller in comparison to the sixth-month visit, which is possibly due to the time needed for the resolution of the inflammatory effects.