The invention provides a lightning protection system for wind turbine blades with optimized injection means of lightning currents in conductive components of their shells. The injection means comprise a current receptor element (27; 47; 67) connected to the input cable of lightning currents and arranged over an area of a shell close to an electrically conductive component (22; 42; 62) and a current injection element (28; 48; 68; 69, 69′) arranged over the electrically conductive component (22; 42; 62) and connected to the current receptor element (27; 47; 67) by at least two distribution cables (31, 32; 51, 52, 53; 71, 72, 73, 74).