This paper deals with the influence of nonlinear frictions to the parametric oscillations of dynamical systems described by the equation with the cubic term at the modulation depth $$\begin{array}{}\text{(0.1)}& x+{\omega }^{2}x+\epsilon (cx+d{x}^3)\cos \gamma t+\epsilon \alpha x^3+\epsilon R(x,\dot{x}),\end{array}$$ where $\omega ,c,d,\alpha$ are constants, $\epsilon$ is a small positive parameter, $R(x,\dot{x})$ is a nonlinear function of $x,\dot{x}$ characterized the frictions considered. Three forms of nonlinear frictions will be investigated here [1, 2]: the Coulomb friction, the turbulent one and their combination. As will be seen later in the analysis, the sign and value of parameter $d$ sharply change the motion picture and the stable regions. It must be emphasized that the equation (0.1) describes the real physical systems more precisely than the one in which $d=0$ [4, 5, 6]. The system of type (0.1) with linear friction was studied qualitatively by Minorsky [3] but no attempt has yet been made to investigate it with the Coulomb friction, turbulent one and their combination.