Adenovirus may cause severe injury of the lung parenchyma, characterized by bronchial epithelium necrosis, interstitial inflammation and alveolar damage, producing pathological alterations like bronchiolitis obliterans and a clinical course known as Postviral Chronical Pulmonary Disease (PCPD). Pulmonary function in these patients is characterized by a fixed and severe bronchial obstruction and alteration of the lung elastic recoll. The aim of this study was to characterize the evolution of pulmonary function in infants with PCPD. Pulmonary function tests were retrospectively analyzed in infants initially and after 6 to 34 months (mean 11.7 mo). A Sensormedics 2600 system was used. Tests were done in patients sedated with chloral hydrate. Compliance(Crs) and Resistance (Rrs) of the respiratory system obtained by the occlusion technique, and Maximal Flow at Functional Residual Capacity (VmaxFRC) obtained by the rapid thoracic-abdominal compression technique were analyzed. Vmax FRC was compared with the theoretical values by the Hanrahan's equation. Relation between Peak Tidal Expiratory Flow and Tidal Volume (PTEF/VT) from the Tidal Flow/Volume Curves were also considered. 12 patients (6 males and 6 females) were included. Mean age at first and second study were 14.5 (range 5 to 22), and 26.2 (range 11 to 54) months respectively. Mean time between both studies was 11.7 (range 6 to 34) months. Results:Table