YouGovPsychonomics predicted 39% of the Hessian electors would vote for German Chancellor Angela Merkel's conservative Christian Democrats (CDU), 23% for the Democratic Party (SPD), 16% for the Free Democratic Party (FDP), 12% for Bündnis 90/The Greens, 6% for Die Linke and 4% for other parties.
The official results for the election on January 18 only marginally deviated from this forecast: the CDU got 37.2%, the SPD got 23.7%, the FDP got 16.2%, Bündnis 90/The Greens got 13.7%, Die Linke got 5.4% and other parties got 3.8% of the votes.
The research firm collated 778 interviews in Hesse, which were conducted online between January 12 and 13 2009.
The company said six other polling companies predicted significantly higher results for the CDU using traditional telephone methods.
Holger Geissler, a member of the executive board, said: "These results reflect the increasing advantages of online research.
"Respondents choose when to participate, are not interrupted and are more honest when answering difficult or sensitive questions and this is reflected in the quality of the data."
Last year, YouGovPolimetrix, YouGov's American company, predicted that Barack Obama would win 52% of the national vote, to John McCain's 46%, which mirrored the presidential result.