 L'Hoest's monkey was formerly included in the genus "Cercopithecus".Molecular studies published by Anthony Tosi in 2003 had raised doubts about the classification of L'Hoest's monkey as a member of the genus "Cercopithecus".The studies indicated that L'Hoest's monkey (along with the others in its species group) is more closely related to the vervet monkeys of the genus "Chlorocebus" and the patas monkey (genus "Erythrocebus") than to the other guenons of the genus "Cercopithecus".