Southeast Europe
This concept is based on the boundaries of the Balkan peninsula. The countries that have been described as being entirely within the region are: Albania, Kosovo, Bosnia and Herzegovina, Bulgaria, Macedonia and Montenegro.
Eurosphere
According to Mark Leonard, the Eurosphere includes 109 countries. In Europe, this includes the 28 member states of the EU, applicant countries wishing to join the EU, the Western Balkans, and European Commonwealth of Independent States countries (including Armenia, Belarus, Georgia, Moldova, Ukraine, and transcontinental Kazakhstan). Curiously he does not mention Western European countries such as Norway who are already integrated into the EU's single market. Outside Europe, he lists every African country and every Middle Eastern country, as well as the countries forming the eastern border of the Eurosphere such as Iran, Azerbaijan, Russia, and Central Asia.