Background: Lung cancer is a common cancer with a high mortality rate. The identification of prognostic factors in lung cancer patients in Vietnam is still limited and inconsistent in clinical practice. Objectives: To describe the clinical, paraclinical characteristics and m-LCPI index in patients with primary non-small cell lung cancer and evaluate the factors affecting overall survival in patients with primary non-small cell lung cancer. Methods: Prospective study of 210 cases of non-small cell lung cancer diagnosed with primary non-small cell lung cancer at the Oncology Department of Hue University of Medicine and Pharmacy Hospital and Hue Central Hospital from February 2020 to February 2023. Results: The majority of hospitalizations were at late stages, from stage IIIA (89%), group 3 and 4 in m-LCPI grading scale constituted the majority (80%). Average overall survival at 3 years was 20.0 ± 14 months, and gradually decreased to 54.8%, 40%, and 38.6% after 1 year, 2 years and 3 years, respectively. Regression analysis of COX model between m-LCPI and OS showed statistical significance with m-LCPI 4 (HR = 3.9, 95%CI = 1.57 - 9.69, p = 0.003), while m-LCPI 3 (HR = 2.44, 95% CI 0.97 - 6.13), p = 0.058) had a weak correlation. Conclusion: Our study shows that 38.6% of patients were still alive after 3 years of diagnosis. m-LCPI index is a good predictor of the patients’ overall survival.