Objective: The majority of lung cancers are diagnosed and treated at an advanced stage. This may, in part, be due to a long lag period between the onset of symptoms, achieving a diagnosis and initiation of treatment. This lag period is highly variable in the limited studies conducted till date and dependent on several modifiable and non-modifiable factors. This study was conducted to determine the average time period required at various steps for diagnosing lung cancer from the onset of symptoms at a tertiary referral centre in Northern India. Methods: Newly diagnosed, histologically proven cases of lung cancer were studied during the period of 2002-08. The delay was calculated as: (a) symptom-to-diagnosis delay, between the onset of symptoms to confirmed diagnosis; (b) diagnosis-to-treatment delay, between diagnosis and treatment started; (c) symptom-to-treatment delay, between onset of symptoms and treatment. Results: Out of 165 patients studied (139 males, mean (SD age,57.6 (8.9 years; 26 females, 53.5 (11.1 years; 84.9% smokers with mean (smoking pack-years of 37 (27.3, 86.7% non small cell lung cancers (NSCLCs) and 13.3% small cell lung cancers (SCLC)). At the time of diagnosis, 90.2% of NSCLC patients had stage IIIB or IV disease, while 81.8% of SCLC patients had extensive metastasis. A total of 28 (17%) patients had received antitubercular treatment (ATT) since onset of current symptoms. The median symptom-to-diagnosis delay, diagnosis-to-treatment delay, and symptom-to-treatment delay was 143 days (range, 4 to 721), 20 days (range, 1-380) and 185 days (18 to 870) respectively. Delay in diagnosis was significantly higher in patients who had received ATT initially (mean difference 65.5 days, 95% confidence interval of difference, 24.46 to 106.6; p= 0.002). Patients with higher KPS score had shorter symptom to diagnosis delay (p=0.075). Conclusion: In comparison with studies from European countries, there is an unacceptable longer lag period from symptom onset to initiation of treatment in Indian patients with lung cancer. Inappropriate treatment with ATT significantly prolongs this delay. These delays need to be shortened to the minimum possible in order to improve prognosis.