This paper contains an analysis of some researches regarding hydraulic systems used for pitch control of wind turbines. As is already known pitch control is important for the aerodynamic efficiency of wind turbine influencing the energy capture, pitch angle being an important parameter by its influence on the angle of attack of the wind. This kind of control is also important in order to protect the turbine in the case of high values of the wind speed reducing the extreme loads. In many cases the system used to change pitch is a hydraulic system. Considering the tendencies in using hydraulic systems in wind turbines, some research directions resulted from reviewed scientific articles. In the case of high-power wind turbines, the load on the blade being important, the rotation of the blades around their own axes in order to change the pitch angle supposes great acting forces. Hydraulic systems provide them in reduce size equipment. The blade rotation may be controlled simultaneously, in the case of collective pitch control, or separately for each one of the blades, in the case of individual control of the blades.