Aim: The early diagnosis and treatment of lung cancer are important for the prognosis of patients with lung cancer. This study was undertaken to investigate patient and doctor delays in the diagnosis and treatment of NSCLC and the factors affecting these delays. Materials and methods: A total of 1016 patients, including 926 (91.1%) males and 90 (8.9%) females with a mean age of 61.5. ±. 10.1 years, were enrolled prospectively in this study between May 2010 and May 2011 from 17 sites in various Turkish provinces. Results: The patient delay was found to be 49.9. ±. 96.9 days, doctor delay was found to be 87.7. ±. 99.6 days, and total delay was found to be 131.3. ±. 135.2 days. The referral delay was found to be 61.6. ±. 127.2 days, diagnostic delay was found to be 20.4. ±. 44.5 days, and treatment delay was found to be 24.4. ±. 54.9 days. When the major factors responsible for these delays were examined, patient delay was found to be more frequent in workers, while referral delay was found to be more frequent in patients living in villages (. p