Survival rates of patients with lung cancer are poor in Denmark and worse than in the other Nordic countries. The study focuses on the diagnostic process, the selection for operation, prognostic factors and outcome in lung cancer. The study comprised 467 consecutive patients with cancer-suspect lesions. In 40% of cases the diagnostic delay exceeded 30 days. Fibreoptic bronchoscopy and fine-needle biopsy (FNB) were the most important diagnostic tests, with approximately 90% accuracy in central and peripheral lesions. FNB of peripheral lesions diagnosed benign histology or small cell lung cancer (SCLC) in 16 patients, and due to that procedure a thoracotomy was prevented. Surgery was performed on 83 (33%) of 252 patients with non-small cell lung cancer. Three-year survival was 37% in all surgically treated patients and 64% after radical operation; 59% of the patients with stage I tumours were alive after three years, but none with stage IV at diagnosis. Among patients operated on, preoperated forced expiratory volume (FEV1) was related to survival rate. Survival rates were higher in women than in men with or without surgery. Of 43 patients with SCLC, 32 received chemotherapy, and half of these were alive after one year. Conclusions from the study were that diagnosis should be speeded up and that diagnostic FNB of peripheral lesions is of value for preventing unnecessary operations. Standard registration of tumour, node, metastasis (TNM) classification, resection, FEV1 (% of predicted) and gender could increase the validity of international comparisons.