Radiotherapy techniques in the last decade evolved to the stage where the potential dose distribution significantly differs from earlier practices. Rotational IMRT, robotic radiotherapy or proton radiotherapy enables extremely precise dose delivery totarget volumes, on the other hand, these techniques can yield a number of problems. As for photon radiotherapy, this concerns primarily the effect of large volume irradiation with doses of 0.1−0.5 Gy. In this range, the hypersensitivity to low doses and the bystander effect may play an important role. Proton therapy is upredictable in its radiobiological effect at the end of the Bragg curve and there is also uncertainty about the peak‘s exact location. These effects should be taken into account when choosing among the irradiation techniques or when applying tolerance doses to critical organs in clinical practice, especially in younger patients with long survival expectation.