In this work we utilize different methods for the calculus of the absorbed dose at different photon and electron energies and we evaluate the difference between their yields. One of these methods is based on the consideration of the factors C lambda e CE (ICRU, HPA, AAPM protocols before 1980); by means of the others (AAPM-Task Group 21, NACP) we seek to obtain a better accuracy introducing new conversion factors. Our measurements were performed using cylindrical and flat ionisation chambers. In the considered energy range we obtained the following results: the new conversion factors have a higher value than C lambda and always smaller than CE.