Croatia is 4.1 times larger than Montenegro.
Area: 56,594 km2 World Factbook
Population: 4,470,534 (July 2014) World Factbook
Croatia, officially the Republic of Croatia, is a unitary democratic parliamentary republic at the crossroads of Central Europe, Southeast Europe, and the Mediterranean. Its capital and largest city is Zagreb. The country is divided into 20 counties and the city of Zagreb. Wikipedia
Area: 13,812 km2 World Factbook
Population: 650,036 (July 2014) World Factbook
Montenegro is a country in Southeastern Europe. It has a coast on the Adriatic Sea to the south-west and is bordered by Croatia to the west, Bosnia and Herzegovina to the northwest, Serbia to the northeast, Kosovo to the east and Albania to the south-east. Wikipedia