We investigate the reduction of a general TeV-scale supersymmetric extra U(
1) model to a 2HDM below the TeV scale through tree level non-decoupling. P
ortions of the parameter space of the extra U(1) model appropriate for obta
ining a 2HDM are identified. Various properties of the resulting 2HDM are c
onnected to the parameter space of the underlying model. [S0556-2821(98)016
23-3].