A simple model has been developed for the generation of theoretical sensitivity and exposure profiles perpendicular to the tomographic plane in computed x-ray tomography. The model incorporates the functional dependence on scanner geometry, focal spot size and shape, and detector sensitivity. The sensitivity and exposure profiles are best depicted as the convolution of functions, when appropriately scaled, describing the focal spot intensity distribution and the transmittance of the pre- and postpatient collimators. Predictions of the model agree well with experimental results on both sensitivity and exposure profiles for small and large nominal slice thicknesses from five different computed tomography (CT) x-ray systems. The CT x-ray systems selected represent both state of the art and older scanner models. Comparisons are also made on the degree of matching of the sensitivity and exposure profiles for each scanner which can be used as a measure of geometrical efficiency in the direction perpendicular to the tomographic plane.