At first junbo was the status which was named accordingly in court ceremony, later it was put to give good treatment to imperial princesses, and there were many examples that imperial princesses who were not married to the emperor were named as a junbo and empress (it is called junbo-rikko [investiture of junbo and empress], and an imperial princess who became an empress in this way is also called a Sonsho kogo [honorific empress who is not a wife of the emperor]).
当初は宮中儀礼において必要に応じて定められた地位であったが、後に皇女の優遇のために置かれるようになり、天皇と配偶関係にない皇女が准母・皇后として冊立された例も多い（これを准母立后と称し、このように后となった内親王を尊称皇后とも呼ぶ）。