Free-breathing 1H MRI offers a means of producing surrogate ventilation images without use of a contrast agent but more validation against direct ventilation imaging methods such as hyperpolarised gas MRI is required. 24 patients with cystic fibrosis were scanned with 1H and 129Xe ventilation MRI. There were strong correlations between 1H ventilation defect percentage (VDP), 129Xe VDP, lung clearance index and FEV1. 1H VDP was typically smaller than 129Xe VDP with wide limits of agreement (LOA) (bias 2.8%, LOA -13.7%, 19.3%). Both similarities and differences between 129Xe and 1H ventilation images were observed across the range of disease severity.