The existence of smooth interfaces was observed to change considerably the confined carriers energy levels and exciton energies in GaN/AlxGa1-xN quantum dots. The results were obtained within the framework of the effective-mass theory. It was observed a shift of the groundstate exciton energy about 27 meV if a 10 Angstrom wide smooth interface exists in a GaN/Al0.3Ga0.7N dot with 50 Angstrom of radius. This is a realistic case considering that interface widths are actually about this magnitude.