A method and an apparatus for controlling a semi-active suspension system (1) for motorcycles are described. According to the present invention, the damping forces applied to controllable force generators (2, 3), such as controllable shock absorbers, provided to the front and the rear semi-active suspensions of a motorcycle are jointly controlled. In particular, the pitch velocity (Vp) of the suspended mass (Ms) is taken into account so as to jointly control the front and rear suspension systems of a motorcycle. The present invention allows the optimization of the global adherence of the motorcycle to the road surface and of the driving and the travelling comfort of the vehicle.