Standing at 2.10 m (6 ft 11 in) Semjonova was the leading women's basketball player in the world in the 1970s and 1980s. Wearing a men's size 21 (US) / 58 (EU) shoe, she was known for having the largest feet ever in women's basketball. For almost all of her playing career, she played for TTT Riga, which was part of Daugava Voluntary Sports Society. With TTT, she won 15 championships in the Soviet Union and the European Champion's Cup 15 times. Semjonova was also very dominant in international play, winning two Olympic Gold medals while playing for the USSR in 1976 and 1980 and never lost a game in official international competition.
She was awarded the Order of the Red Banner of Labour in 1976, and in 1993 became the first non-US woman enshrined into the Basketball Hall of Fame.She was an inaugural member of the Women's Basketball Hall of Fame in the class of 1999. In 2007, she was enshrined in the FIBA Hall of Fame. During the 2007 Latvian Sportspersonality of the year award ceremony, Semjonova received the Lifetime Contribution to Sport award.