The diocese is a suffragan in the ecclesiastical province of the Metropolitan Archbishop of Utrecht.

The only minor basilica is Basiliek van de H. Liduina en Onze Lieve Vrouw van de Rozenkrans, dedicated to St. Liduina and Our Lady of the Rosary, in Schiedam.

It enjoyed a papal visit from Pope John Paul II in May 1985.

As per 2014, it pastorally served 531,600 Catholics (14.5% of 3,655,000 total, mainly protestants and atheists) on 3,403 km2 in 75 parishes, with 358 priests (110 diocesan, 248 religious), 34 deacons, 452 lay religious (289 brothers, 163 sisters) and 6 seminarians.

(all Roman Rite) The official website of the diocese shows the Catholic communities organized in two vicariates (also known as deaneries).