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UNLABELLED Aim of the study was to evaluate the influence of different spiral-CT parameters for the visualisation of vascular stenoses, especially of the renal arteries. MATERIAL AND METHODS Models with a density equivalent to that of fat, filled with diluted contrast agent, and an inner lumen of 4, 6, 8 mm were scanned in x-, y- and z-direction. Data were acquired in up to 24 second long spiral-CT scans using different spiral-CT parameters (collimation, table speed, reconstruction algorithm, tube current). Detection of the degree of stenosis was achieved by assessment of the axial images and 3D reconstructions. RESULTS The best correlation between real and measured degree of stenosis was seen by using a small collimation, a low table increment and assessment of the axial images reconstructed in standard algorithm. The stenosis degrees of models directed in x- and y-direction were overestimated and those in z-direction were underestimated depending on the spiral-CT parameters. CONCLUSION For optimal imaging of renal artery stenoses, collimation of 2 mm (pitch = 1-2 and a reconstruction interval of 1 mm is recommended.