In the first centuries of Christianity a meeting of small communities was considered as the way of resolving conflicts, making important decisions, and seeking God’s will for the community. With the increasing number of believers followed necessary decentralization of ecclesiastical structures so that dioceses could decide on administrative and organizational matters. Clergy assemblies have served these issues and we can consider them today as prefiguration of diocesan synods. Most authors believe that the first diocesan synod assembly took place in France in Auxerre in A.D 578. Over the centuries, the institution of diocesan synod experienced both the flourish moments, as well as the crises. For its definitive fixation in the canonical doctrine should be considered the treaty of Pope Benedict XIV De Synodo Dioecesana published in 1748. The value of the diocesan synod as a legal institution has been confirmed by the Second Vatican Council, which in the Decree Christus Dominus has expressed the wish of synodal fathers that the institution will take on a new life and serve the Church in modern times. The current legislation concerning the diocesan synod is contained in the Code of Canon Law (c. 460-468), as well as in the Instruction of the diocesan synods issued in 1997 by two Vatican congregations. In Poland since the promulgation of the Code in 1983, until the year 2012 31 diocesan synods were held. Some of them took place in the days of communism, the other in a free Poland, which also had an impact on their course. In addition to many historical, ecclesial and pastoral circumstances particularly important was the influence of St. John Paul II,who personally participated in the opening or closing of some diocesan synods.