Background: The prognostic role of thyroid transcription factor-1 (TTF-1) expression in lung cancer has been assessed but with inconsistent results. The present study aimed to evaluate the prognostic value of TTF1 expression in advanced non-squamous non-small cell lung cancer (NSCLC). Materials and Methods: In this retrospective study, patients with stage IIIB-IV non-squamous NSCLC were enrolled. Progression free survival (PFS) and overall survival (OS) were assessed according to TTF1 expression status, age categories (≤60 vs >60 years), gender, performance status (PS) (0-2 vs 3-4), type of 1st line chemotherapy (pemetrexed containing vs others) and EGFR status. Results: A total of 120 patients were included. In univariate analysis, PFS was improved in patients with PS 0-2 (7.0 vs 2.0 months, p=0.002) and those who received pemetrexed-containing chemotherapy (