Abstract: The properties of ultracold atomic Bose-Fermi mixtures in external potentials are investigated and the existence of gap solitons of Bose-Fermi mixtures in optical lattices demonstrated. Using a self-consistent approach we compute the energy spectrum and show that gap solitons can be viewed as matter-wave realizations of quantum dots and antidots with the bosonic density playing the role of trapping expulsive potential for the fermions. The fermionic states trapped in the condensate are shown to be at the bottom of the Fermi sea and therefore well protected from thermal decoherence. Energy levels, filling factors, and parameters’ dependence of gap soliton quantum dots are also calculated both numerically and analytically.