In this work we studied the response of two different Victoreen instruments as a function of the exposure rate, the instrument orientation and photon energy. The rate dependence for both instruments is of the order of 8 % over the range of exposure rates tested (0.5 mR/h to 1000 mR/h). Regarding the instrument orientation dependence investigation, a significant difference is observed between the two instruments. While the Victoreen 451P shows no significant dependence with instrument orientation, the Victoreen 451P-DE-SI shows a significant dependence of up to 20 % between the three different orientations. Finally, the energy dependence measurements of both instruments reveal that the instruments measure lower exposure rate values compared to the reference values for the low energy x-rays by about 20 %. While, for the 60Co gamma-ray beam measurements, both instruments are about 5 % higher than the reference value.