Objective: To summarize and analyze the clinical characteristics, differential diagnosis, treatment and prognosis of patients with second primary non-small cell lung cancer (second primary non-small cell lung cancer), and to provide reference for the diagnosis and standardized treatment of second primary lung cancer in the future. Methods: The clinical data of 44 patients with second primary non-small cell lung cancer admitted to our hospital from January 1995 to October 2010 were collected to summarize their pathogenesis and clinicopathological characteristics, and to analyze the diagnosis, treatment and prognostic factors of second primary lung cancer. Results: Among the 44 patients with second primary non-small cell lung cancer, 24 were male and 20 were female; the median age of onset of second primary lung cancer was 56 years; 12 cases had concurrent cancer and 32 cases had heterochronic cancer, and the median interval between two primary cancers was 28 months. Imaging features such as “burr, lobar and mediastinal lymph node fusion and enlargement” and pathological features such as TTF-1(+) and CK7+/CK20- in the new nodules in the lung helped the differential diagnosis. Treatment of second primary non-small cell lung cancer was the same as that of primary lung cancer, with treatment selected according to stage, and 19 patients are still alive with a maximum survival of 86 months; 12 patients were treated with EGFR-TKIs at different treatment stages, with a median survival of 26.5 months, which is better than that of patients not treated with EGFR-TKIs (median survival of 15 months, P = 0.038). CONCLUSIONS: The diagnosis of second primary non-small cell lung cancer is dependent on pathological diagnosis, the treatment principles and prognosis are the same as those of primary lung cancer, and the combination of multiple therapies can help prolong the survival of patients.