In this paper, we review two popular finite difference schemes for solving the Poisson equation in 2-D domains. First, we introduce the standard five-point discretization scheme. An error analysis is also given to show that the accuracy of the five-point scheme is O(h^2 ), where h is the grid size of the spatial discretization. We then introduce a ninepoint finite difference scheme which is O(h^4) accurate. Numerical experiments are carried out to demonstrate the theoretical analysis.