The issue of executive power sharing in democratic countries with a monarch as head of state has received little scholarly attention. In many ways this make perfect sense; since there is no place for a powerful hereditary monarch in a democratic system, one could argue that systems with powerful monarchs do not qualify as democracies. Nevertheless, there are many examples of political systems, classified as democracies by most reputable categorizations or indices, where the monarch has, or has had, more or less the same position as a president in semi-presidential systems. The aim of the present study is to study to what extent the occurrence of semi-constitutional monarchies, i.e. democratic regimes in which power is shared between a prime minister and a monarch, can be explained by reference to Huntington’s notion of the King’s dilemma and the size of countries. The study is global and encompasses the time period 1800–2017.