This paper focuses on the maximization of the torque-to-weight ratio of permanent magnet synchronous motors (PMSM) using a topology optimization method. It aims at finding the optimal design that either maximizes the torque for a given weight or minimizes the weight for a required torque. The analysis presented in this paper besides considers radial and tangential permanent magnets. The paper shows that the optimization always leads to the same optimal motor topology, which is scaled to achieve the required torque. In addition, a scale law is highlighted for computing the PMSM torque according to its size and is used to plot a Pareto curve that provides the achievable torque-to-weight ratio according to the motor weight.