We present highly accurate configuration interaction results for two nonrelativistic electrons confined within a sphere and interacting via a Coulomb force. In such a system, the radius of the sphere R can be considered as a measure of the strenght of the electronic repulsion. So, distinct correlation regimes, from the noninteracting limit to a high correlated regime, can be achieved by varying R. The results clearly show how very high correlation effects might appear in the system. Energies, density distributions, conditional probabilities and the exchange-correlation hole have been evaluated for different values of R. The essentially exact results here presented can be used as benchmarks for new exchange-correlation functionals and/or other approximate methods. (C) 2003 American Institute of Physics.