A system for displaying lung ventilation information, the system comprising an input (12) and a processing unit (15). The input being provided for receiving multiple CT images (71) of a lung, each CT image (71) corresponding to one phase of at least two different phases in a respiratory cycle. The processing unit (15) being configured to compare CT images (71) corresponding to different phases in the respiratory cycle for determining a deformation vector field for each phase, to generate for each phase a ventilation image (72) based on the corresponding deformation vector field, to spatially align the ventilation images (72), and to generate for at least one common position (62) in each one of the aligned ventilation images (72), a function (81) of a time course of a ventilation value for said common position (62), each ventilation value in the function (81) being based on the deformation vector fields corresponding to the aligned ventilation images (73).