Our purpose was to determine the repeatability of squamous cell cancer in head and neck (SCCHN) and muscle tissue vascularity measurements as well as the inter- and intra-observer agreement using dynamic contrast-enhanced (DCE) multi-detector CT (MDCT). Twelve patients with histologically proven SCCHN were twice examined within 46 h. Measurement error and repeatability were assessed for each of the four functional parameters using the Bland-Altman plots. Two independent observers recorded the vascularity values of the tumor tissue; inter- and intra-observer agreement was assessed using the Bland-Altman plot analysis and intraclass correlation coefficients. For the tumor, the mean difference (95% limits of agreement) was 0.40 ml/min/100 g tissue (-6.80, 9.60); 0.01 (-0.96, 0.97) ml/100 g tissue; 0.20 (-1.80, 2.30) s; and 0.40 (-2.00, 2.80) ml/min/100 g tissue for BF, BV, MTT, and PS, respectively. For the muscle, the mean difference (95% limits of agreement) was -0.18 (-1.70, 1.35), 0.04 (-1.17, 1.35), -0.10 (-5.80, 5.60), and -0.10 (-2.20, 2.00), respectively. Measurement changes of at least +/-8%, 30%, 36%, and 13% were found to be significant for BF, BV, MTT, and PS, respectively. There was better intra- than inter-observer agreement.