This paper refers to the possibility of realizing m-D FIR and IIR discrete systems either by using non-recursive techniques based on direct convolution or by recursive techniques. The general response formula of an arbitrary m-D IIR system is given in terms of a number of finite convolutions, which involve the past input values as well as the set of initial input and output values. These sets of initial conditions are also explicitly given in the general case. The above results may be used for the development of block realization models of m-D systems, which are characterized by high degree of parallelism and low computational cost (due to the use of FFT and fast convolution techniques).