Image quality and dose produced by a spiral CT with various pitch values were investigated on the basis of test-object images and measurements of CT dose indexes. No major difference in image quality or dose was observed when comparing sequential and spiral mode acquisition with a pitch of one. Increase in pitch value produces a loss of contrast which leads to a loss of detectability. Nevertheless, in realistic protocols the image quality in the transverse plane remains acceptable up to pitch values of 1.3-1.6.