Purpose: 1) to determine the level of post-traumatic stress disorder (PTSD) by means of impact of event scale (IES) in patients for whom lung cancer has been diagnosed for the first time and compare this level in patients having learnt that they affected by chronic obstructive pulmonary disease (COPD); 2) to compare PTSD in patients and their significant others facing a diagnosis of lung cancer; 3) to determine whether or not IES and General Health Questionnaire 28 (GHQ-28) correlate. Methods: This prospective survey-study included 41 consecutive patients who learnt that they were afflicted by primary lung cancer. IES and GHQ-28 were answered once between four and five weeks following medical appointment. The significant others (n = 16) who were present during the lung cancer diagnostic appointment were also invited to complete similar questionnaires. Control group consisted of 19 patients with chronic asthma or COPD. Results: Following a lung cancer diagnosis, patients and their significant others are indistinctly affected by a high level of PTSD. These two groups had a higher frequency of high IES total score when compared with COPD patients. The IES intrusion subscale score significantly differed among groups: median [IR] values: 20 [12 - 26]; 15 [9 - 22]; 7 [5 - 15] for significant others, cancer patients and COPD patients respectively; P = 0.02). IES and GHQ-28 inversely correlated. Conclusion: Patients and significant others facing a diagnosis of lung cancer are at high risk of PTSD. The level of IES intrusion in persons facing lung cancer increases emotional distress that in turn affects quality of life.