There are various methods to compute electromagnetic scattering by arbitrarily shaped particles. The aim of this article is merely to give a short introduction to three very different types of methods and have a look at the applicabilities and shortcomings of each. At first some comments are made. • to the Discrete Dipole Approximation (DDA), alias Coupled Dipole Method (CDM), as a special form of the Volume Integral Equation Method (VIE); • to the Finite Difference Time Domain (FDTD) and • to the Extended Boundary Condition Method (EBCM). As an example the results and the parameters of different codes for a cube are compared to give just a hint of the computational demands.