The majority of patients who receive a diagnosis of DIPNECH are middle-aged, nonsmoking women, and two different modes of clinical presentation have been described. In a subset of patients, the disease is an incidental finding during the investigation for another disorder, most frequently a malignant disease. In this case, the patient is usually asymptomatic and may have normal pulmonary function tests. Small, multiple, noncalcified pulmonary nodules are the most common, if not the only, HRCT scan finding. Most frequently, however, patients who receive a diagnosis of DIPNECH are frankly symptomatic at the time of diagnosis and have clinical, radiologic, and pathologic evidence of constrictive bronchiolitis. The clinical history of such patients includes almost invariably cough and dyspnea that have worsened slowly over years. As the clinical symptoms are nonspecific, they are frequently attributed to gastroesophageal reflux, asthma, or COPD and may be present for years before a correct diagnosis is made. Pulmonary function testing shows either an obstructive defect with no response to bronchodilators or a mixed pattern. The association of mosaic attenuation with small, multiple, noncalcified pulmonary nodules represents the typical CT scan pattern, and bronchiectases or bronchiolectases can be seen. Expiratory scans usually show multiple areas of air trapping, thus suggesting an airways obstruction as the cause of the mosaicism. The number of pulmonary nodules may seem scarce in some patients, but techniques such as maximum intensity projection or volume rendering of multidetector CT scan data may help detect the true profusion of such nodules, which is usually high.