We report the systemic cytokine and chemokine response in children with the 2009 pandemic influenza A (H1N1) virus infection. In patients with pneumonia, the serum levels of IFN-γ and IL-5 were significantly higher than those in patients without pneumonia. This tendency was also present for IL-6, IL-8, IL-10, IL-13, and MCP-1 in patients with pneumonia. Among patients with pneumonia, the levels of MCP-1 were significantly higher in the group of patients with pneumonia with severe respiratory failure than patients with mild pneumonia.