The therapeutic efficiency of an anti-inflammatory agent, dexamethasone (DXM), and a nitric oxide synthase (NOS) inhibitor, Nitro-L-arginine methyl ester (L-NAME), in lung tissue injury after lung contusion was investigated. Serum levels of tumor necrosis factor-alpha (TNF-alpha), interleukin-10 (IL-10), YKL-40, an inflammatory peptide, inducible NOS (iNOS), and Clara cell protein 16 (CC-16) were evaluated. Immunohistochemical analyses were also performed, and the lung tissue was examined histopathologically. The study consisted of eight groups of Sprague-Dawley rats (n = 10 in each group), weighing 250-300 g: (1) control, (2) contusion, (3) control + DXM, (4) contusion + DXM, (5) control + L-NAME (6) contusion + L-NAME, (7) control + DXM + L-NAME, and (8) contusion + DXM + L-NAME. A previously developed lung contusion model was used, in addition to the control group. The rats were administered DXM and L-NAME intraperitoneally (i.p.) at doses of 15 and 60 mg/kg/day, respectively. DXM and L-NAME administration decreased the iNOS level in the contusion groups. DXM increased the levels of YKL-40 and IL-10 in both the control and contusion groups, with higher levels in the contusion groups. L-NAME increased the serum level of IL-10 in the lung contusion groups. DXM increased the synthesis of CC-16 in the control and contusion groups. The combined use of a high-dose steroid and NOS inhibitor resulted in the death of the rats. Steroids can increase the level of cytokines, such as YKL-40 and IL-10, and the synthesis of CC-16 and prevent pneumonia, ALI/ARDS, and sepsis in lung contusion.