Quantitative analyses of hyperpolarized gas and 1H lung MRI together provide quantitative information on lung obstruction. Quantification requires segmentation of the ventilated and non-ventilated regions of the hyperpolarized gas MRI and definition of the lung cavity from the paired 1H MRI. Spatial fuzzy c-means segmentation was developed to segment these image pairs simultaneously. Error measures with respect to manual reference segmentations and qualitative grading showed significant improvements when compared to an established method. This work may help towards standardisation and automation of lung ventilation image analysis, and help improve accuracy and reproducibility.