Demand Side Management (DSM) has been become a popular option for improving electricity system operations and reliability. Moreover, Demand Response (DR) programs provide superior efficiency and flexibility to their users. This paper proposes a method to assess system reliability and evaluate the specific contributions made by spinning reserves (SR) and DR. The method structurally and spatially decomposes the reliability index Expected Energy Not Supplied (EENS) at the nodal level. The method can identify nodes suitable to implementing DR programs. Numerical example of a six-node system demonstrates the effectiveness of the proposed evaluative method.