The authors report on cross-sectional scanning tunneling microscopy/scanning tunneling spectroscopy and subsequent electronic wave-function imaging at a low temperature (T=77 K) on cleaved In(Ga)As/GaAs quantum dots (QDs). The dI/dV spectra exhibit a set of discrete and well-defined peaks in the QD conduction band. Differential conductance dI/dV maps, obtained on a series of individual dots, display clearly the real space spatial variation at the nanometer scale of the envelope (amplitude) of the electron wave functions for the successive ground state and excited states. Wave-function symmetry of the first two excited states are identified in the STS measurements. (C) 2009 American Vacuum Society. [DOI: 10.1116/1.3013854]