In the present study, the radiation-induced effect of cytochrome c (CytC) and vitamin C (VitC) is studied with respect to survival of MCF-7 cancer cells grown in aerated media. Both, CytC and VitC, were incubated with MCF-7 cancer cells under various concentrations individually, as well as in mixture and cells were subsequently treated with γ-ray in a dose range of 0 to 30 Gy. Generally, an increase of cell survival was observed under substance treatment up to a radiation dose of 5 Gy compared to the control group. Based on the obtained results it is believed that cell survival depends strongly on the action of free radicals produced at the given concentration of the incubated CytC and VitC as well as on the specific reaction rate constants (k: l mol(-1) s(-1)) of the involved processes.