Lung diseases imply a high consumption of healthcare resources representing a burden for patients and their families as well as for the society. The aim of the Global Outcomes in Lung Diseases (GOLD) study was to perform a cost-of-illness analysis of three pathologies affecting the lower respiratory tract: community-acquired pneumonia (CAP), chronic obstructive pulmonary disease (COPD) and bronchial asthma (BA). This observational study was conducted in a large region of northeast Italy, Triveneto, between 1999 and 2000. Patients of both sexes and aged > or = 14 years, were randomly selected from 28 identified centres of pneumology; patients were considered eligible if they had been visited at least twice at the centre during the observational period. Study periods were different for the three pathologies: for BA and COPD the recruitment period lasted 8 weeks and the follow-up period 12 months; for CAP, given the acute nature of the disease, two recruitment periods (May and November) were identified with a follow-up lasting 6 months. After collecting information for each patient (age, sex, risk factors, severity of the disease, occupation), data were recorded by each centre in a dedicated software program and then sent to a central database where final results were analysed. Cost-of-illness analysis was conducted within the framework of the National Healthcare System (NHS). Consumption of medical resources used during the follow-up period was valued according to market prices and published official tariffs. A total number of 1068 patients (596 men and 458 women) were selected: 42.5% were affected by BA, 46.3% by COPD, and 11.2% by CAP. Mean cost per patient/year for patients affected by BA and COPD ranged from Euro 608 to 2457 and from Euro 1500 to 3912, respectively, depending on illness severity. Mean cost per episode of CAP was Euro 1586. This study confirms the findings of other studies published in the international literature, demonstrating that asthma and COPD are often misdiagnosed and mistreated and so their management, especially for the most severe patients, becomes complex and highly expensive. The use of preventive, specialised care could help in achieving early diagnosis and treatment of these patients.