The present study focuses on the behavior analysis of different lattice structures in spur gears. The aim of this study is to compare the mechanical characteristics of various additively manufactured lattice structures when used as the main body of spur gears, compared to a solid gear body. Three different lattice structures were designed, simulated and topologically optimized, in order to generate a spur gear that has similar mechanical characteristics but better strength/weight ratio and others. Characteristics were quantified by measuring the maximum and mean, stress and deformation and calculating their weight ratios. Out of the three lattices, two lattices showed exceptional mechanical characteristics for the application. The Octahedral lattice showed the best stress/weight ratio while in the Double Pyramid lattice, the maximum deformation/weight ratio was observed. This study concludes that lattice structures when used in spur gears can have positive effects in weight reduction but also reveal new characteristics, suited for specific applications. The reported work provides important contributions to the possible applications of lattice structured spur gears. Such results could have huge benefits for a wide range of applications where either the lowest possible stress/weight ratio is required for maximum strength, or a high deformation/weight ratio is required to provide a damping effect for gear transmission applications for which the reduction of vibrations is critical. Furthermore, lattice structured gears showed increased heat dissipation compared to solid gears.