Group A (n = 34) consisted of patients with community acquired pneumonia (CAP) likely to be caused by extracellural bacteria. Seventeen had microbiological evidence of pulmonary infection, with isolation of the offending pathogens from sputum, blood or BAL samples (when bronchoscopy was performed). Seventeen patients were diagnosed with CAP on the basis of typical clinical and radiological presentation and good response to antibiotic therapy. Main radiological Group B (n = 34) consisted of patients with non-bacterial respiratory disorders. Diagnoses were: lung cancer (13 patients); pulmonary embolism (six patients); interstitial lung disease (six patients); heart failure (n = 5); pulmonary tuberculosis (two patients); rheumatoid pleuritis (one patient); and Q-fever (one patient). Main radiological findings were: right pulmonary infiltrate (six patients); left pulmonary infiltrate (three patients); bilateral pulmonary infiltrates (11 patients); right pleural effusion (four patients); left pleural effusion (one patient); both right lung infiltrate and right pleural effusion (four patients); both left lung infiltrates and left pleural effusion (two patients); bilateral pulmonary infiltrates and left pleural effusion (one patient); and left pulmonary infiltrate and bilateral pleural effusions (one patient).