A phantom consisting of a human skull fixed in a cylinder containing water was used to study the occurrence of artifacts and their influence on image quality in CT of the posterior fossa. Only minor differences in interpetrous bone artifact and in deviation in CT numbers in other parts of the posterior fossa were found between eight tested scanner models. Interpetrous bone artifact was not significantly affected by slice thickness but it could be reduced to some extent by proper selection of the scan angle and almost eliminated by application of a dual-energy technique. Other bone-related artifacts, however, were found to be dependent on slice thickness.