At the 2000 Summer Olympics she competed in 5000 metres, but she has participated in shorter races since, now competing mainly in the 1500 metres. On 31 July 2008, Tomashova was suspended by the IAAF, along with six other Russian track and field athletes, for doping offences. She was charged under IAAF rules 32.2 (b) and 32.2 (e) for a "fraudulent substitution of urine which is both a prohibited method and also a form of tampering with the doping control process".
She was set to compete in the 2008 Summer Olympics.
On 20 October 2008, it was announced that Tomashova, along with six other Russian athletes would receive two-year doping bans for manipulating drug samples. 800 metres - 2:02.09 minimum (2012)
1000 metres - 2:34.91 minimum (2005)
1500 metres - 3:56.91 minimum (2006)
3000 metres - 8:25.56 minimum (2001)
5000 metres - 14:39.22 minimum (2001).