We aimed to investigate the delays from the first symptom to thoracotomy and to examine whether the delays cause the stage advancement in lung cancer. This prospective study included 138 patients with non-small cell lung carcinoma who underwent thoracotomy. Clinical files of the patients were analyzed and a questionnaire was created to obtain information from the patients. The mean duration values were 81.3 days for the application interval, 61.3 days for the referral interval, 20.3 days for the diagnostic interval, and 21.9 days for the treatment interval. The application interval was longer than 30 days (patient delay) in 50 patients (37.9 %). The mean interval from the first visit to doctor to thoracotomy was 97.2 days. There was a doctor delay in 102 (73.9 %) patients; a referral delay in 83 patients (60.1 %), a diagnostic delay in 47 patients (36.4 %), and a treatment delay in 96 patients (69.6 %). The mean total duration was 176.2 days. Ninety-four patients (71.2 %) had a total delay. Mean total delay was 184.5 days in pathologic stage I, 187.3 days in stage II, 167.7 days in stage IIIA, 142.6 days in stage IIIB, and 150.3 days in stage IV (p>0.05). Delays during the course between the first symptom and thoracotomy in lung cancer patients were a common problem among our patients. Prolonged durations in the application and referral of patients are the most significant cause of delays. Presence of delay or length of delay did not correlate with pathologic tumour stage in this study.