This work is focused on derivation of numerical methods for partial differential equations of anisotropic and isotropic diffusion. We are using principles of finite volume method to find numerical solution of anisotropic Poisson equation in two-dimensional and three-dimensional space domain with Dirichlet boundary condition. Solution is designed for general non-uniform polygonal grids. The scheme is implemented on non-uniform logically rectangular grids and its experimental order of convergence is determined.