Errors encountered in the capacitance-voltage (C-V) measurements of quantum well (QW) structures are usually attributed to Debye smearing. The other sources from which errors may occur are not well discussed in literature. In this paper we have highlighted the limits of C-V measurements on QW structures. Simulations have been carried out through the self-consistent solutions of the Schrödinger and Poisson equations for various band offsets, dopings, and temperatures. This will provide guidelines for suitable design of quantum structures for proper C-V measurements.