A set of simulations has been performed to investigate the spatial resolution and count density requirements for brain SPECT imaging. Projections were drawn from a matrix representation of the Hoffman brain phantom. These projections were convolved with realistic point spread functions and Poisson noise was added to simulate a wide range of imaging situations normalized to a fixed imaging time. The projections were optimally smoothed with a Wiener filter and were reconstructed with a ramp filter. The quality of the reconstructed images was determined objectively from the normalized mean square between the simulated data and the true distribution. This ranking was validated against the preferences of a group of trained observers. The results from this study indicate that the optimal choice of spatial resolution (collimation) depends on the available count density.