Bronchiectasis is common in developing countries, but its precise underlying mechanism can be detected in only about 40% of the cases. The studies reporting the frequency of atopy and its relation to radiological findings and lung function in bronchiectasis are limited in number, and the results are controversial. The present study was designed to investigate the relationship between atopy and bronchiectasis by means of high resolution computed tomography (HRCT) and pulmonary function tests. Skin prick test, HRCT and pulmonary function tests, including spirometric values of forced expiratory volume in one second (FEV1), FEV1/FVC (forced vital capacity) ratio were performed in 121 bronchiectatic patients of unknown etiology and in 68 healthy controls. Atopy and HRCT scores for the severity of atopy and extent of bronchiectasis respectively were determined for each patient. The rate of atopy (48.8% vs 11.8%) and mean atopy score (14.3 +/- 10.1 mm vs 5.5 +/- 2.1 mm) were significantly higher in patients with bronchiectasis than those in controls. Atopic patients had significantly worse spirometric values and more extended bronchiectasis than non-atopics. There is a significant correlation between atopy and HRCT scores (r = 0.54, p < 0.001), indicating that the more severe atopy is the more extended bronchiectasis. In conclusion, we suggest that the rate of atopy is higher in bronchiectatic patients than that in healthy controls. Bronchiectatic patients with atopy have lower spirometric values and higher HRCT scores. Atopy might be considered as a deteriorating and/or a causative or contributing factor for development of bronchiectasis.