The International Theological Comission looked at the Diaconate over a five year period, (per ZENIT article) and also looked at Deaconesses: vatican.va/roman_curia/congregations/cfaith/cti_documents/rc_con_cfaith_pro_05072004_diaconate_en.html
"The general secretary of the International Theological Commission, Father Georges Cottier, O.P., has responded to certain questions about the Commission’s study of the diaconate raised by the October 8th issue of La Croix. Fr. Cottier stated that the Commission’s study has not concluded that the possibility that women could be ordained to the diaconate remains open, as asserted by La Croix, but rather tends to support the exclusion of this possibility.
The Commission of theologians, even if it has not the role of pronouncing with the authority, which is characteristic of the Magisterium, presented two important indications which emerge from study of the matter. In the first place, the Commission observed that the deaconesses mentioned in the tradition of the early Church cannot simply be assimilated to ordained deacons. In support of this conclusion, Fr. Cottier noted that both the rite of institution and the functions exercised by deaconesses distinguished them from ordained deacons.
Furthermore, Fr. Cottier noted that the Commission’s study reaffirmed the unity of the sacrament of Holy Orders. The distinction between the ministry of bishops and priests, on the one hand, and that of deacons, on the other hand, is nonetheless embraced within the unity of the sacrament of Holy Orders. The Commission’s reaffirmation of this teaching arose from a careful study of the ecclesial tradition, of the documents of the Second Vatican Council, and of the postconciliar Magisterium of the Church.
Fr. Cottier stated that “it belongs to the Magisterium to pronounce with authority on the question, taking into account the historical and theological research presented by the study of the International Theological Commission.”
The International Theological Commission devoted over five years of research to the topic of the history and theology of the diaconate before approving the text of its study at its recently concluded meeting. The study was produced at the request of the Congregation for the Doctrine of the Faith."
Bold text by me.