Michael Moore, an MP since 1997, was defence spokesman before being promoted to the foreign affairs role, succeeding Sir Menzies Campbell.
He is also the deputy leader of the Scottish Liberal Democrats and the governor and vice-chairman of the Westminster Foundation for Democracy.
Before speaking on defence issues, Mr Moore was a junior foreign affairs spokesman.
He chaired the party's 1999 Scottish election campaign and spent two years as transport spokesman leading up to the 2001 election, before becoming the Lib Dem spokesman on Scottish affairs.
On the libertarian wing of the party, Mr Moore was once a parliamentary researcher and is a qualified accountant.