This paper presents a messy genetic-algorithm-based optimization scheme for SVC planning, aimed at voltage stability enhancement of power systems under most critical and N-1 operation conditions. The SVC placement was formulated as a multi-objective optimization problem in terms of maximum worst-case reactive power margin, highest load voltages towards the critical operating points, minimum real power losses, and lowest SVC device costs. During the genetic algorithm search for the optimal solution, the most critical disturbance scenario was estimated with each SVC placement and the configuration of the original power system. The preselected candidate was further checked against the N-1 security criterion.