Rome and Istanbul have been for centuries the seats of two of the main religious centres of the western hemisphere: the Papacy and the Caliphate, entities with both significant spiritual and temporal power. During the 19th and the 20th centuries, these institutions underwent significant changes in a context of state secularization: in the case of the Papacy, there was a loss of temporal power and its 'reduction' to a mainly moral authority; the Caliphate, on the other hand, was abolished after World War I, succeeded by the Presidency of Religious Affairs (Diyanet), a bureaucratic body under state control, founded in the era of Kemalist secularism. Despite these changes, today both institutions still play a significant role in the public life and public policies of the Italian and the Turkish republics. While the Vatican is able to influence the Italian public sphere and public discourse through both its influence on common people and its lobbying activities in relation to political decision-makers, in Turkey the Diyanet has become the main tool in the reshaping of Turkish society (both by the Kemalists and, later, by Erdoğan's AKP). This paper will analyze their influence on the two countries' public policies in relation to religious pluralism and to family-related issues, to show how different ideas of secularism, institutional arrangements and historical paths have led to a very different role of the two institutions in the Italian and Turkish political system.