Photoinduced magnetization has been recently evidenced by Hashimoto et al. in CoFe Prussian blue analogues. We synthesized three compounds with a variable cobalt environment to point out the conditions required to observe the photoinduced magnetization. Structure and electronic structure of the compounds have been investigated combining XANES, infrared spectroscopy, and powder X-ray diffraction experiments. Magnetization as a function of temperature before and after irradiation showed that diamagnetic pairs Co-III-NC-Fe-II are necessary for the existence of the photoinduced magnetization, but their presence is not a sufficient condition. The role of hexacyanoferrate vacancies in the phenomenon is pointed out.