Websites Habbo Hotel and Lola's Land are featuring adverts for the vaccine, which protects against human papillomavirus (HPV).
HPV is a sexually-transmitted infection that causes most cases of cervical cancer.
Adverts and text on the Lola's Land website for young girls say: "Remember chica, this is a totally life-saving, revolutionary vaccine! Let's fight cervical cancer together and arm ourselves against it!"
The text of the advert reads: "If you're in Year 8, arm yourself against cervical cancer."
Adverts and Q&A-style features have also been put on the Habbo Hotel "virtual world" website.
Schools across the UK will start vaccinating pupils aged 12 and 13 from this week with about 300,000 girls receiving the jab in England alone.
By July 2011, more than two million girls will have been offered the vaccine, including those up to the age of 18 as part of a catch-up programme.
The Government's campaign for England includes online, press, TV and radio advertising.
Girls aged 17 and 18, who form part of the catch-up programme, will be the target of a different advertising campaign in October.
What do you think about the Government's cervical cancer vaccine drive? Are there any other ways the government could have targeted young people? Your comments: (Terms and conditions apply)
"Disappointed that they chose the vaccine that only covers two strains of HPV rather than 4 strains. A perfect opportunity missed again because in my view the government does not want to spend any more money and if they had chosen Gardasil there would have been a push from the public to offer vaccine to boys. Boys should be vaccinated too..... The campaign does not give clear signposting to research on Cervarix and what you find is not specific to 13-year-old girls - this is why as a mum of a 13-year-old I will be holding off vaccinating my daughter this year." - Name and address supplied