The purpose of this study was to register the accuracy and reproducibility of the multidetector computed tomography (MDCT) estimate of hypopharyngeal and laryngeal tumor volumes. Eighteen consecutive patients with larynx or hypopharynx squamous cell carcinoma were enrolled in this prospective trial, scheduled for surgery and examined by MDCT. A total of 72 tumor volume measurements were reported by two different operators, one of them in three different sessions, using the sum-of-areas method. The results were compared with the volume calculated by surgical sampling. The mean tumor volume measured by MDCT was 5.7 +/- 9.3 ml (range 0.1-41.6). The mean volume measured from the surgical specimens was 5.6 +/- 8.6 ml (range 0.06-33.6). The level of agreement between histological and MDCT volumes was high, with a slight tendency of MDCT to overestimation, proportional to the size. The analysis of interoperator variability showed a tendency of the more expert operator to make more accurate estimates, but the differences were not significant (P = 0.62, 0.75 and 0.63). The evaluation of the three different sessions of the less expert operator revealed a good repeatability. According to our study, MDCT estimate of tumor volume is an effective, reproducible method. MDCT tends to produce more dispersed results in case of large tumors.