Marfan syndrome is a genetic disorder of the connective tissue, including involvement of the lungs. Pulmonary function test was performed in 32 asymptomatic adult Marfan patients using European Community for Coal and Steel (ECCS) and Global Lung Function Initiative (GLI) reference values. Using GLI equations for reference, significantly lower lung function values were noted for forced vital capacity (FVC) (87.0 +- 16.6% vs. 97.1 +- 16.9%; P < 0.01) and forced expiratory volume in the first second (FEV1) (79.6 +- 18.9% vs. 88.0 +- 19.1%; P < 0.01) predicted compared to ECCS. Obstructive ventilatory pattern was present in 25% of the cases when calculating with GLI lower limit of normal (LLN), and it was significantly more common in men as compared to women (n 5 6, 50% vs. n 5 2, 10%; P 5 0.03). GLI is more suitable to detect early ventilatory changes including airway obstruction in young patients with special anatomic features, and should be used as a standard way of evaluation in asymptomatic Marfan population.  Kulcsszavak: Marfan syndrome, lung function, spirometry, reference values, Global Lung Function Initiative