PURPOSE: It is essential to know the functional and morphologic changes of the larynx in the evaluation of laryngeal lesions. Conventional CT which has relatively long examination time is not suitable for this aim. The purposes of this study are to evaluate the capability of spiral CT in the dynamic study of the larynx and to know whether this new technique can replace conventional laryngography or not. MATERIALS AND METHODS: Five healthy volunteers and 20 patients with laryngeal lesions underwent spiral dynamic CT scans with 3-dimensional reconstruction of the mucosal surface. A series of spiral CT scans were done while the volunteers performed various laryngeal positions to obtain the functional and morphologic information. The maneuvers used were:quite breathing, "E" phonation, Valsalva maneuver, modified Valsalva maneuver, and a new method of our own, "modified breath holding" technique. The patients were scanned when in quite breathing. Additioal scans were obtained by using the "modified breath holding" technique. RESULTS: The dynamic study with spiral CT could provide high resolutional images which nicely depicted the mobility of vocal cords and the mucosal changes of the laryngeal cavity in both healthy volunteer and patient groups. In patient group, the new "modified breath holding" technique was easier and more reproducible than other maneuvers. CONCLUSION: Spiral CT allows a dynamic study of the larynx and can be a new alternative of laryngography.