Lung cancer is the most common neoplasm on over the world and remains the leading cause of cancer death in both men and women. The predominant cause of lung cancer is exposure to tobacco smoke. The methods using for diagnosis and monitoring of the disease are based on radiological, cytological and histopathological examinations. The prognosis for survival in lung cancer is very poor which is mostly caused by late diagnosis when the disease gets the last phases. The prevention methods used for early detection of lung cancer include X-ray chest examination, cytological sputum examination and chest computer tomography (CT). In that article we present the case of history of 55 years old patient, heavy smoker, who was admitted to the hospital because of tumour of right lung and right hilus showed on chest X-ray. The bronchoscope revealed extended changes in bronchium for the left lower lobe, which were not present on chest X-ray but only in later done CT. If there were no changes in right lung, probably the diagnostic examinations in that patient, with high risk of lung cancer, would be performed much later. That is because the present guidelines do not recommend that low-dose CT should be used to screen for lung cancer.