Pulmonary function test is the most common diagnostic method to evaluate the integrated mechanical capacity of lung ventilation. This test can help to assess the conditions of airway diseases such as asthma and chronic obstructive pulmonary disease (COPD). The constricted airways in these diseases disturb the normal stream of respiratory flow and cause heterogeneous ventilation leading to ventilation-perfusion mismatch affecting gas exchange.1,2 However, none of the lung ventilation models to-date presented the lung function test in the full conducting airway geometry. The goal of the current study is to simulate the lung function test using one dimensional (1D) ventilation model and to demonstrate the difference between a normal and a constricted lung models. One dimensional (1D) centerlines of central airways were obtained from patient-specific geometry segmented from CT images. Then, the skeletons of conducting airways down to terminal bronchioles were generated using a volume-filling branching algorithm within the lung surface boundary.3 In addition to the normal case, the bronchoconstricted lung was modelled by reducing radii of selected airways. To compute the dynamic pressure distribution, a fully coupled mathematical model including acinar tissue deformation and airway network flow was introduced.4 We assumed quiet breathing and minimal airway wall compliance to simplify the model. For the input boundary condition, a wave representing the changes in pleural pressure during the lung function test was imposed on each acinar unit. Flow volume and flow rate during inhalation and exhalation were computed to test the function of the model. The respiratory flow in the normal lung model showed a physiologically reasonable level of lung capacity. Both peak flow rate and tidal volume decreased in the bronchoconstricted lung model. According to the reduction of the lung capacity, heterogeneity in ventilation was increased in the constricted airway model. Computed parameters of the lung function test such as FEV1, FVC and FEV1/FVC in the normal lung were in the clinically acceptable range for the healthy subjects. But, those values were notably decreased by bronchoconstriction. The inspiratory flow-volume curves showed typical shape of normal and constricted lung curves as reported in clinical measurements. We simulated pulmonary function tests in normal and bronchoconstricted lungs. The pulmonary function of the lung model weakened as the constriction and ventilation heterogeneity increased. The ventilation model presented in this study could be an effective tool to assess respiratory flow characteristics and increase our understanding of the lung function.