204 nations competed at the 2012 Olympics:
A
Afghanistan
Albania
Algeria
American Samoa
Andorra
Angola
Antigua and Barbuda
Argentina
Armenia
Aruba
Australia
Austria
Azerbaijan
B
Bahamas
Bahrain
Bangladesh
Barbados
Belarus
Belgium
Belize
Benin
Bermuda
Bhutan
Bolivia
Botswana
Brazil
British Virgin Islands
Brunei
Bulgaria
Burkina Faso
Burundi
C
Cambodia
Cameroon
Canada
Cape Verde
Cayman Islands
Chad
Chile
China
Chinese Taipei
Colombia
Comoros
Congo
Cook Islands
Costa Rica
Ivory Coast
Croatia
Cuba
Cyprus
Czech Republic
D
Denmark
Djibouti
Dominica
Dominican Republic
DR Congo
E
Ecuador
Egypt
El Salvador
Equatorial Guinea
Eritrea
Estonia
Ethiopia
F
Federated States of Micronesia
Fiji
Finland
France
G
Gabon
The Gambia
Georgia
Germany
Ghana
Great Britain
Greece
Grenada
Guam
Guatemala
Guinea
Guinea-Bissau
Guyana
H
Haiti
Honduras
Hong Kong
Hungary
I
Iceland
Independent Olympic Athletes
India
Indonesia
Iran
Iraq
Ireland
Israel
Italy
J
Jamaica
Japan
Jordan
K
Kazakhstan
Kenya
Kiribati
Kuwait
Kyrgyzstan
L
Laos
Latvia
Lebanon
Lesotho
Liberia
Libya
Liechtenstein
Lithuania
Luxembourg
M
Macedonia
Madagascar
Malawi
Malaysia
Maldives
Mali
Malta
Marshall Islands
Mauritania
Mauritius
Mexico
Moldova
Monaco
Mongolia
Montenegro
Morocco
Mozambique
Myanmar
N
Namibia
Nauru
Nepal
Netherlands
New Zealand
Nicaragua
Niger
Nigeria
North Korea
Norway
O
Oman
P
Pakistan
Palau
Palestine
Panama
Papua New Guinea
Paraguay
Peru
Philippines
Poland
Portugal
Puerto Rico
Q
Qatar
R
Romania
Russia
Rwanda
S
Saint Kitts and Nevis
Saint Lucia
Saint Vincent and the Grenadines
Samoa
San Marino
São Tomé and Príncipe
Saudi Arabia
Senegal
Serbia
Seychelles
Sierra Leone
Singapore
Slovakia
Slovenia
Solomon Islands
Somalia
South Africa
South Korea
Spain
Sri Lanka
Sudan
Suriname
Swaziland
Sweden
Switzerland
Syria
T
Tajikistan
Tanzania
Thailand
Timor-Leste
Togo
Tonga
Trinidad and Tobago
Tunisia
Turkey
Turkmenistan
Tuvalu
U
Uganda
Ukraine
United States
Uruguay
Uzbekistan
V
Vanuatu
Venezuela
Vietnam
Virgin Islands
Y
Yemen
Z
Zambia
Zimbabwe
205 nations are participating in 2010 Youth Olympic Games.
There are 200 countries at the 2010 olympics.
there r 204 countries represented in the Beijing Olympics
all of them
Brazil
204
88 countries competed in the 2010 olympics.
There was 88 countries at the 2014 olympics. 6 more countries than at the 2010 Olympics.
There are no summer Olympics in 2010.
204
15
35 Nations