Parishes in the Diocese of Cloyne are being restricted to between 10 and 25 tickets each for today's ordination of Canon William Crean (60).
Diocesan sources said this was unavoidable, given the limited space available within St Colman's Cathedral in Cobh, Co Cork.
Almost 150 clerics will attend, led by the Papal Nuncio Archbishop Charles Brown, the Archbishop of Cashel & Emly Dr Dermot Clifford and Archbishop of Dublin Dr Diarmuid Martin.
The cathedral has a capacity of around 600 but the diocese has 46 parishes, 107 churches and a population of over 150,000.