We apply the exact numerical diagonalization technique to study two interacting electrons in a one-dimensional parabolic quantum dot. We consider a modified Coulomb interaction potential between the electrons with a truncation parameter that serves to regularize the behaviour of the bare Coulomb potential in one dimension. We report the dependence of ground and excited state energies for several values of the truncation parameter as the strength of electronic correlations is varied relative to the confinement energy. The similarity of this quantum dot system to the ammonia molecule is pointed out. © IOP Publishing Ltd.