Background <p>The present study aims to evaluate the utility of Cystatin C testing for differentiating lung cancer from benign nodules of the lung in patient.</p> Methods <p>Consecutive patients were enrolled in our research who had undergone a surgical resection or with fine needle biopsy between April 2015 and June 2024. All the patients were evaluated with their age, sex, smoking, drinking, and histology of lung cancer. Serum levels of Cystatin C in patients with lung nodules were evaluated using an automated analyzer.</p> Results <p>540 consecutive patients were enrolled in our research. There were 443 patients with primary lung cancer and 97 patients diagnosed as benign nodules. The serum level of Cys-C in patient with malignant nodule was significantly higher than in those with benign nodule (<i>p</i>&lt;0.01), but they were comparable between patients with squamous cell carcinoma, adenocarcinoma, small cell lung cancer and large cell neuroendocrine carcinoma. Moreover, receiver operating characteristic curve analysis showed that a Cys-C level&gt;0.92&#xa0;mg/L was a good predictor for ruling out benign nodule, with a sensitivity of 64.0% and a specificity of 63%.</p> Conclusions <p>Our study suggests that the serum Cys-C level test may be helpful for differentiating lung cancer from the benign nodule of the lung in patient.</p>