It is well known that in order to obtain a uniform dose in the treated volume as defined in ICRU 50, there should be a 10% maximum difference between maximum and minimum dose values in treatment planning. Clinical target volume (CTV) should be related to external areas of body sections where tumour is located. These areas are important because different radiation beams enter through them. Therefore, verification of the planning target volume (PTV) through the external areas is highly significant. In this work we point out the importance of controlling that PTV is irradiated as planned considering some error sources usually found in radiotherapy practice with equipment that has been intensively used for a long time. Moreover, I think this experience will be helpful for those centers around the world where radiation treatment is carried out with reconditioned units. (author).