Purpose Post-therapy imaging of 90Y-Bremsstrahlung x-rays using SPECT, although 90Y is not the best isotope for imaging, has the potential of providing a reliable activity distribution of the 90Y-microspheres inside the liver. In literature, several image acquisition parameters and subsequent different reconstruction protocols can be found. With the aim of obtaining an optimized 90Y-Bremsstrahlung SPECT image, two reconstruction methods, Filtered-Backprojection (FBP) and Ordered-Subsets-Expectation-Maximization (OSEM), were applied both to phantoms and post-therapeutic images using several reconstruction parameters. Methods A 90Y-Bremsstrahlung image of a water filled Jaszczak phantom was acquired. A line source containing 222 MBq of 90Y and uniformly distributed activity was placed inside, along the longitudinal axis. The image was acquired using a gamma camera (e.cam, Siemens) equipped with a MEGP parallel-hole collimator and an energy window of 136–184 keV. By modifying the order and critical frequency (FBP) and number of iterations, subsets and Gaussian-filter FWHM (OSEM), SPECT resolution, image contrast, noise and counts per voxel ( C voxel ) were obtained from the phantom images. 24 different reconstruction protocols (10 FBP and 14 OSEM) were used and compared. Results The results of the reconstruction methodologies evaluated showed that in the FBP algorithm, improving the image resolution implies a loss of contrast and an increase of the noise. Regarding the OSEM algorithm, an increase of the noise level occurs with a higher number of iterations, although both contrast and image resolution improved. In addition, the C voxel also depends on the reconstruction algorithm parameters. It was showed that the C voxel is strongly connected with noise, and that increasing the noise also increases the C voxel . Conclusion Although in the past FBP algorithms were thoroughly used as standard methods for SPECT reconstruction, nowadays, iterative methods can be used in an acceptable reconstruction time due to an increase in computer performance and, often, present better quantitative and qualitative results. Still, optimization is required to provide the best trade-off between noise/contrast and image resolution. Nevertheless, the availability of FBP reconstruction algorithms is still desirable due to the higher number of parameters (e.g. different filters).