In this paper the state-space realization results of  for causal 2-D systems are generalized to a much larger class of 2-D systems. We introduce a generalized notion of a state-space realization for which the state can still be recursively evaluated. The results include a realization method for a class of NSHP filters. In the second part we introduce inverse 2-D systems with inherent delay. Some results concerning existence of an inverse with inherent delay for a 2-D system will be given. It will be shown that, in general, a causal 2-D system cannot have a causal inverse (with inherent delay). Furthermore, it will be shown that a causal 2-D system always has an inverse with inherent delay in the larger class of 2-D systems mentioned above.