In patients with so-called roentgenologically occult intraluminal lung tumours, an accurate assessment of tumour size, its location and peribronchial tumour extent is important prior to any intraluminal bronchoscopic therapy (IBT) with curative intent. In twenty patients with so-called occult early-stage lung cancers, clinical outcome was compared to high resolution computed tomography (HRCT) findings prior to IBT. HRCT showed peribronchial tumour extension or nodal enlargement in 7 of the 20 patients (35%), and consequently treatment policy was changed. Five of the seven died 1.5-6 months after diagnosis, one patient underwent a radical pneumonectomy after induction chemotherapy, and the remaining patient is alive with pleural metastasis. HRCT showed intraluminal tumours in 11 of the 20 patients and IBT with curative intent was given. Complete response (CR) was achieved in 10 of the 11 patients, follow-up has been 4-26 months. One patient underwent a radical lobectomy, pathological stage T1NO, after 3 months because of tumour recurrence. HRCT was inconclusive in 2 of the 20 patients with postobstructive infiltrates. IBT was unsuccessful in both these cases. High resolution computed tomography may provide supportive evidence of intra-and extraluminal tumour; thereby, helping in the assessment of patients who were judged to be suitable for intra-luminal bronchoscopic therapy with curative intent. This may lead to a change in the treatment policy. High resolution computed tomography findings are complementary to bronchoscopic, histological and cytological examinations for the proper evaluation of treatment indications in patients with occult lung cancer.