Abstract. In this paper we study the existence of non-trivial solutions for equations driven by a non-local integrodifferential operator~$\mathcal L_K$ with homogeneous Dirichlet boundary conditions. More precisely, we consider the problem $$\left\{ egin{array}{ll} \mathcal L_K u+\lambda u+f(x,u)=0 & {\mbox{ in }} \Omega\ u=0 & {\mbox{ in }} \RR^n\setminus \Omega\,, \end{array} ight.$$ where $\lambda$ is a real parameter and the nonlinear term $f$ satisfies superlinear and subcritical growth conditions at zero and at infinity. This equation has a variational nature, and so its solutions can be found as critical points of the energy functional $\mathcal J_\lambda$ associated to the problem. Here we get such critical points using both the Mountain Pass Theorem and the Linking Theorem, respectively when $\lambda<\lambda_1$ and $\lambda\geq \lambda_1$\,, where $\lambda_1$ denotes the first eigenvalue of the operator $-\mathcal L_K$. As a particular case, we derive an existence theorem for the following equation driven by the fractional Laplacian $$\left\{ egin{array}{ll} (-\Delta)^s u-\lambda u=f(x,u) & {\mbox{ in }} \Omega\ u=0 & {\mbox{ in }} \RR^n\setminus \Omega\,. \end{array} ight.$$ Thus, the results presented here may be seen as the extension of some classical nonlinear analysis theorems to the case of fractional operators.