Different configurations of leaky-wave antennas (LWAs) based on graphene metasurfaces are studied. The electronic properties of a graphene metasurface in the low THz range are investigated in details in order to discuss the reconfigurability features of the presented structures. A simple exact formula for evaluating the ohmic losses related to the surface plasmon polariton (SPP) propagation along a suspended graphene sheet is given. This allows us to explain the low efficiency of reconfigurable antennas based on SPPs along graphene metasurfaces. Then, the radiative performance and relevant losses of graphene Fabry-Perot cavity antennas (FPCAs) based on leaky waves (LWs) are investigated in details and compared to previous solutions based on SPPs. In particular, a single-layer structure, i.e., a grounded dielectric slab covered with a graphene metasurface, and a multilayered structure, i.e., a substrate …