Puerto Rico competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This was the nation's fifteenth consecutive appearance at the Olympics.
Ukraine competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This was the nation's third consecutive appearance at the Summer Olympics in the post-Soviet era. The National Olympic Committee of Ukraine sent the nation's largest ever delegation to these Games. A total of 240 athletes, 125 men and 115 women, took part in 21 sports. Women's handball was the only team-based sport in which Ukraine had its representation at these Games for the first time. There was only a single competitor in modern pentathlon and taekwondo.
Poland competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This was the nation's eighteenth appearance at the Summer Olympics, except the 1984 Summer Olympics in Los Angeles, because of the Soviet boycott. The Polish Olympic Committee sent a total of 194 athletes to the Games, 132 men and 62 women, to compete in 21 sports. Men's volleyball was the only team-based sport in which Poland had its representation in these Olympic Games. There was only a single competitor in women's taekwondo.
Finland competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. Finnish athletes have competed at every Olympic Games since its debut in 1908. The Finnish Olympic Committee sent the nation's smallest ever team to the Games after the 1932 Summer Olympics in Los Angeles. A total of 53 athletes, 36 men and 17 women, competed only in 12 sports; the nation's team size was roughly denser from Sydney by a quarter of the athletes.
Bulgaria competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This was the nation's seventeenth appearance at the Summer Olympics, except for three occasions, including the 1984 Summer Olympics in Los Angeles, because of the Soviet boycott. The Bulgarian Olympic Committee sent 95 athletes, 49 men and 46 women, to compete in 19 sports. Shooting champion and four-time Olympian Mariya Grozdeva became the nation's first ever female flag bearer in the opening ceremony.
Romania competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. Romanian athletes have competed at every Summer Olympic Games since its official debut in 1924, missing only two editions, including the 1948 Summer Olympics. The Romanian Olympic and Sports Committee sent the nation's smallest team to the Games since the 1988 Summer Olympics in Seoul. A total of 108 athletes, 50 men and 58 women, had competed in 16 different sports, most notably in artistic gymnastics and rowing. For the third time in Olympic history, Romania was again represented by more female than male athletes.
Israel competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. It was the nation's thirteenth appearance at the Summer Olympics.
Peru competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This was the nation's fifteenth appearance at the Olympics, except the 1952 Summer Olympics in Helsinki.
Mongolia competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This was the nation's tenth appearance at the Olympics, except the 1984 Summer Olympics in Los Angeles, because of its partial support to the Soviet boycott.
Colombia competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This was the nation's sixteenth appearance at the Olympics, except the 1952 Summer Olympics in Helsinki.
Latvia competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This was the nation's eighth appearance at the Summer Olympics.
Slovakia competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This was the nation's third consecutive appearance at the Summer Olympics since the post-Czechoslovak era. The Slovak Olympic Committee sent a total of 64 athletes to the Games, 48 men and 16 women, to compete in 11 sports. There was only a single competitor in artistic and trampoline gymnastics and sailing.
Venezuela competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This was the nation's fifteenth consecutive appearance at the Olympics, since its debut in 1948. A total of 48 athletes, 33 men and 15 women, competed in 15 sports.
Kyrgyzstan competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This was the nation's third appearance at the Olympics in the post-Soviet era.
Barbados competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This nation marked its ninth appearance at the Olympics, except the 1980 Summer Olympics in Moscow because of the United States boycott.
Turkmenistan competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004.
Lithuania competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This was the nation's sixth appearance at the Summer Olympics. The National Olympic Committee of Lithuania sent the nation's smallest delegation to the Games since the 1992 Summer Olympics in Barcelona. A total of 59 athletes, 47 men and 12 women, competed in 13 sports, including the men's basketball team as the nation's team-based sport.
Uzbekistan competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This was the nation's third consecutive appearance at the Olympics. The National Olympic Committee of the Republic of Uzbekistan sent a total of 70 athletes to the Games, 52 men and 18 women, to compete in 13 different sports, tying its delegation record with Sydney four years earlier. There was only a single competitor in road cycling, artistic and trampoline gymnastics, and table tennis.
Moldova competed at the 2004 Summer Olympics in Athens, from 13 to 29 August 2004. This was the nation's third consecutive appearance at the Summer Olympics in the post-Soviet era.
Ecuador competed at the 2012 Summer Olympics in London, from 27 July to 12 August 2012. This was the nation's twelfth consecutive appearance at the Olympics. It had first competed at the 1924 Summer Olympics in Paris.
Russian Empire (1900–1912)
Soviet Union (1952–1988)
Unified Team (1992)
