The banks scored an average of 36% in the survey, compared to the 81% average for the 10 largest international banks, included in the peer group.
The 54 largest Russian companies surveyed by S&P's earlier this year scored 50% on average, 14 percentage points higher than the largest Russian banks.
"These results suggest that regulators, in tandem with participants in the capital markets, should continue to apply pressure to banks in order to raise the transparency of the banking sector, which needs to open up to investors, depositors and the general public," S&P's Director of Governance Services Julia Kochetygova said.
"The biggest gaps in Russian banks' disclosure include the identity of beneficial owners (only 16% of total private-stake ownership is disclosed) and information about related-party transactions, corporate governance structure and procedures such as risk management policies," Kochetygova said.
"Standard & Poor's also found that too few banks have board-level audit committees and that timely publication of international annual financial statements is lacking, with only 10 of the banks publishing 2004 IFRS and/or U.S. GAAP financials before July 2005," she said.
The survey, conducted as an Standard & Poor's research project, was supported by the Russia Banking Corporate Governance Project of the International Finance Corporation, the British Embassy in Russia and the U.S. Agency for International Development.
The survey is only based on public information, primarily looking at disclosure from the point of view of an international investor, the agency said.