The aim of this study was to clarify whether the diaphragm in patients with COPD (emphysema dominant type) can be evaluated by abdominal ultrasonography. We therefore established a method for diaphragm scanning: The dome of the right hemidiaphragm was detected by epigastric right oblique scan passing through the right edge of the inferior vena cava and the zone of apposition. Diaphragmatic flattening, correlation between the flattening and %FEV1.0, diaphragmatic motion, and the inspiratory time cycle were also measured. We studied 14 patients with COPD (emphysema dominant type) and 12 healthy control subjects. RESULTS: (i) Diaphragmatic flattening was recognized in patients with COPD and the radius of the right hemidiaphragmatic curvature (index of diaphragmatic flattening) correlated with %FEV1.0. (ii) Motion of the anterior diaphragm was poor in patients with COPD. (iii) Expiration time was prolonged in patients with COPD. CONCLUSION: Flattening and motion of the diaphragm, as well as the prolonged expiratory time were possible to evaluate by abdominal ultrasonography. Diaphragmatic flattening reflects %FEV1.0. Based on these observations we believe that abdominal ultrasonography may be useful to avoid underdiagnosis of COPD.