Bronchoscopic evaluation of stenosis is limited due to radial distortion of bronchoscopic images and the unknown distance between the endoscope and the stenotic area. The purpose of this study was the development and validation of a method for measuring cross-sectional areas in large airways. Distance measurements were performed using a laser probe inserted into the working channel of a bronchoscope. The laser probe was positioned to the locus of interest in the airway, a ring of light (helium/neon) projected on to the luminal wall and the images acquired using an electronic bronchoscope. The images taken were distortion-corrected by means of a computer program. The method was validated by simulating airways using tubes of known diameter. Additionally, distortion-corrected bronchoscopic images were compared with distortion-free videoscopic image analysis of tracheal slices taken from pigs. In the case of the plastic tubes, Pearson's correlation coefficient (r) as well as the intraclass correlation coefficient (ICC) were slightly higher (r=0.99, p<0.01, ICC=0.97) than the correlation of cross-sectional areas between bronchoscopic and videoscopic images of tracheal slices (r=0.88, p<0.01, ICC=0.87). This concept allows accurate and reproducible determination of cross-sectional areas in large airways.