The structure of mobile telecommunication markets varies considerably across Europe, ranging from monopolies with a handful of subscribers to markets with five operators and many millions of subscribers. Where competitive markets occur, there is also an incumbent operator possessing substantial first mover advantages. This paper explores these advantages, asking whether the incumbent has remained the largest operator as the market has developed. This question is investigated using data from 49 European countries. The analysis finds that in most countries the incumbent continues to be the largest operator measured by market share. In some countries, later entrants into the market have struggled to gain market share, contributing to the highly concentrated nature of many mobile markets. The extent to which the geographical footprint of an operator influences its market share is also examined.