The Cl-HCl radical complex is investigated by a combination of accurate ab initio
quantum chemical methods for the evaluation of the three lowest electronic potential
energy surfaces and non-adiabatic couplings between them, and 
quantum evaluation of vibronic states using 
wavefunction propagation in imaginary time within a close coupling scheme.
The sensitivity of the vibronic energies on the quality of the potential surfaces is clearly
demonstrated. Moreover, it is shown, that non-adiabatic couplings between the three lowest
electronic states play an important role, especially for highly excited vibronic states.
Since under experimental conditions the complex is 
prepared in a superposition of excited vibronic 
states close to the dissociation limit, 
the inclusion of non-adiabatic effects is crucial for a quantitative 
interpretation of future higher resolution spectroscopic experiments.