Amorphous selenium photodetectors, in both lateral and vertical structures, have been investigated for indirect conversion medical imaging applications. The low dark current, high responsivity for blue light, and possibility for gain are all among the attractive features of these devices. Typically these devices are deposited on a solid glass substrate and are read out using thin-film-transistors (TFTs). With the advent of flexible TFTs, flexible electronics have become a viable technology. This technology may be leveraged for flexible imaging, however the detection and conversion materials that serve to convert the incident x-rays to collectable charge will also need to be flexible. In this paper, we investigate the use of amorphous selenium photodetectors on flexible substrates and compare their performance with amorphous selenium photodetectors deposited on glass.