The binding energies of hydrogenic donor in both finite and infinite GaAs-(Ga,Al)As spherical quantum dots are calculated as a function of the donor position for different radii within the effective-mass approximation. It is observed an enhancement of the binding energy of donors in quantum dots when compared to results in quantum wells and quantum-well wires, which is an expected consequence of the higher geometrical electronic confinement in these systems. The density of impurity states as a function of the donor binding energy was also calculated. As a general feature it presents structures associated with special impurity positions that may be important in the understanding of the absorption and photoluminescence experiments of doped quantum dots.