Organising pneumonia (OP) is usually promptly responsive to corticosteroid treatment. We describe a series of 3 cases of severe, progressive, biopsy-proven fibrosing OP causing respiratory failure. All cases presented with peribronchial and subpleural consolidations, had a fibro-inflammatory infiltrative component in the alveolar septa, and only had a partial and unsatisfactory response to corticosteroids. However, they responded to mycophenolic acid (MPA) treatment with resolution of respiratory failure as well as clinical and functional improvement. MPA as an additional treatment option for aggressive forms of fibrosing OP and interstitial lung disease needs to be further explored.