In this study, real-time imaging using γ-emitting nuclide, 109Cd, was studied and sensitivity and resolution of the system we developed was evaluated. When RI was applied to the plant, the radiation from the RI distributed throughout the plant was converted to visible light by a scintillator. Then, this weak light was multiplied by a micro-channel plate(MCP)and photographed by a charge-coupled device(CCD)camera. 109Cd emits 88keV γ-rays together with 22keV X-rays, and therefore it is necessary to investigate effective condition for designing an observation system for the measurement of radiation from 109Cd. Analysis was performed to determine which rays, γ-rays or X-rays, were mainly detected by this system and the optimal scintillator thickness for imaging 109Cd was investigated. Then the sensitivity and resolution of the system was evaluated.