On most ethical theories, interpersonal comparisons of well-being matter for some decisions, and on some ethical theories, interpersonal comparisons matter for all decisions. But there are very challenging questions about how we can compare the well-being of different individuals. In this presentation, I review how new developments in brain imaging might impact our ability to compare positive and negative experiences across individuals. I argue that brain imaging technology is likely to be able to solve some challenges related to interpersonal comparisons, though not the most challenging philosophical objections. And, even putting aside these objections, I suggest there are particular challenges with comparing positive and negative experiences.