Treated metal oxide particles include metal oxide particles treated with at least a charge modifying agent. The charge modifying agent is represented by the following formula: An-Zc—Yb—Ar(EW)a wherein Ar represents an aromatic group, EW represents an electron withdrawing group, Y represents a spacer group, Z represents an alkylene group, An represents an anchor group, a is an integer from 1 to 5, b is 0 or 1, and c is 0 or 1. The treated metal oxide particles may also be treated with a second charge modifying agent or with a hydrophobicity-imparting agent. A toner composition including toner particles and treated metal oxide particles is also disclosed.