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.
Chinese Taipei competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. "Chinese Taipei" was the designated name used by Taiwan to participate in some international organizations and almost all sporting events, including the Olympic Games. Neither the common name "Taiwan" nor the official name "Republic of China" would be used primarily due to opposition from the People's Republic of China. This also was the nation's eighth consecutive appearance at the Olympics.
Belarus competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This was the nation's fifth appearance at the Summer Olympics in the post-Soviet era. The Belarus Olympic Committee sent a total of 151 athletes to the Games, 82 men and 69 women, to compete in 22 sports.
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.
Hong Kong competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. It was the territory's thirteenth appearance at the Olympics and, at the opening ceremony, its team was the last to enter the stadium before the host nation because of the use of the Greek alphabet.
Sweden competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This nation has competed at every Summer Olympic Games in the modern era, except for the 1904 Summer Olympics in St. Louis. The Swedish Olympic Committee sent the nation's smallest team to the Games since the 1976 Summer Olympics in Montreal. A total of 115 athletes, 62 men and 53 women, competed only in 20 different sports. Women's football was the only team-based sport in which Sweden had its representation at these Games. There was only a single competitor in boxing, diving, artistic gymnastics, judo, modern pentathlon, and rowing.
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.
Denmark competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004.
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.
Czech Republic competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This was the nation's third appearance at the Summer Olympics after gaining its independence from the former Czechoslovakia. The Czech Olympic Committee sent the nation's largest team to the Games since the post-Czechoslovak era. A total of 142 athletes, 80 men and 62 women, competed in 19 sports; the nation's team size was roughly denser from Sydney by one sixth of the athletes. Women's basketball was the only team-based sport in which the Czech Republic had its representation at these Olympic Games. There was only a single competitor in equestrian, artistic and trampoline gymnastics, judo, and weightlifting.
Slovenia competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This was the nation's fourth consecutive appearance at the Summer Olympics since the post-Yugoslav era. The Slovenian Olympic Committee sent the nation's largest ever delegation to the Games in Olympic history. A total of 79 athletes, 56 men and 23 women, competed in 10 sports. For the second consecutive time, men's handball was the only team-based sport in which Slovenia had its representation at these Games.
Hungary competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. Hungarian athletes have competed at every Summer Olympic Games in the modern era, except the 1920 Summer Olympics in Antwerp, and the 1984 Summer Olympics in Los Angeles because of the Soviet boycott. The Hungarian Olympic Committee sent a total of 209 athletes to the Games, 119 men and 90 women, to compete in 20 sports. Water polo and handball were the only team-based sports in which Hungary had its representation in these Olympic Games. There was only a single competitor in road cycling and mountain biking.
Thailand competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This was the nation's thirteenth appearance at the Olympics, except the 1980 Summer Olympics in Moscow because of its partial support to the United States boycott.
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.
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.
Serbia and Montenegro competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. Previously known as the Federal Republic of Yugoslavia, this was the nation's third and last joint appearance at the Summer Olympics before Serbia and Montenegro became separated independent states in 2006. The Olympic Committee of Serbia and Montenegro sent a total of 85 athletes to the Games, 78 men and 7 women, to compete in 14 sports. Men's basketball, football, volleyball, and water polo were the only team-based sports in which Serbia and Montenegro had its representation at these Games. There was only a single competitor in road cycling, judo, tennis, and wrestling.
Croatia competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This was the nation's fourth consecutive appearance at the Summer Olympics since the post-Yugoslav era. The Croatian Olympic Committee sent the nation's smallest delegation to the Games since its debut in 1992. A total of 81 athletes, 66 men and 15 women, competed in 14 sports. Men's water polo, and men's handball were the only team-based sports in which Croatia had its representation in these Olympic Games.
Uruguay competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. This was the nation's eighteenth appearance at the Olympics, except the 1980 Summer Olympics in Moscow, because of its full support to the United States boycott.
Switzerland competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. Swiss athletes competed at every Summer Olympic Games in the modern era, except when they boycotted the 1956 Summer Olympics in Melbourne as a protest to the Soviet invasion of Hungary. The Swiss Olympic Association sent a total of 98 athletes to the Games, 59 men and 39 women, to compete in 18 sports.
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.
