PURPOSE: In stereotactic radiosurgery, awareness of the precise localization and volumetry of tumors and of critical organs, and the planning of the treatment field are important. The purpose of this study was to determine the degree of distortion in images obtained by digital subtraction angiography(DSA) and to assess whether DSA is a suitable may substitute for MRI in the planning of stereotactic radiosurgery. MATERIALS AND METHODS: After designing DSA phantoms we obtained images under variable conditions and analyzed image distortion using an image analysis program. RESULT: DSA imaging distortion increased as intensifying tube size became greater and the distance between tube and object decreased. CONCLUSION: Images obtained by DSA imaging were very distorted, and in the planning of stereotactic radio-surgery DSA is not, therefore, a suitable substitute for MRI.