We consider a utilitarian planner with the power to design a discrete choice set for a heterogeneous population with bounded rationality. We find that optimal paternalism is subtle. The policy that most effectively constrains or influences choices depends on the preference distribution of the population and on the choice probabilities conditional on preferences that measure the suboptimality of behavior. We first consider the planning problem in abstraction. We next examine policy choice when individuals measure utility with additive random error and maximize mismeasured rather than actual utility. We then analyze a class of problems of binary treatment choice under uncertainty. Here we suppose that a planner can mandate a treatment conditional on publicly observed personal covariates or can decentralize decision making, enabling persons to choose their own treatments. Bounded rationality may take the form of deviations between subjective personal beliefs and objective probabilities of uncertain outcomes. We apply our analysis to clinical decision making in medicine. Having documented that optimization of paternalism requires the planner to possess extensive knowledge that is rarely available, we address the difficult problem of paternalistic policy choice when the planner is boundedly rational.