Substituted Al clusters with 8 atom, which is trivalent but smaller than Al atom, or with covalent C atom were investigated using photoelectron spectroscopy (PES). In Aln-mBm- (n greater than or equal to 5 for m = 1, n greater than or equal to 10 for m = 2), three valence electrons of each B atom as well as Al atom contribute to electron shell structures, while the C atom strongly binds two free electrons from Al-n(-) in AlnC- (n = 5-30). The substitution with B atom allowed us to determine that s-p mixing starts at n = 6 in pure Al clusters. Perturbed electron shells and the geometry of Al12B1- Al11B2-. and Al12C- are discussed.