If the outlook for prices and the economy is expected to improve the BOJ will need to consider whether "adjustments in the level of interest rates will be necessary," one board member said.
Another board member said the BOJ should examine the policy effects and the possible side effects of ETF purchases from "every angle" because of rising stock prices and earnings.
Japan's growth this year has exceeded some economists' expectations, and its stock markets have rallied due to rising corporate earnings, causing some traders to question whether the BOJ should rein in its aggressive monetary easing.
"Consumer spending is doing well, supported by rising stock markets. The BOJ's policy focus is on interest rates, so it is only natural to question its purchases of risk assets," said Hiroshi Miyazaki, senior economist at Mitsubishi UFJ Morgan Stanley Securities.
The summary of opinions does not identify individual speakers, and it is unclear whether a majority of the BOJ's nine-person board shares these views.
Governor Haruhiko Kuroda also said clearly last week that as long as consumer prices remain distant from the BOJ's 2 percent inflation target he does not want to raise rates.
The BOJ board's comments were published against a background of solid economic growth and robust industrial production.
Japan's industrial output rose a more-than-expected 0.6 percent in November, and retail sales rose 2.2 percent in November from a year earlier, more than the median forecast for a 1.2 percent increase, government data showed on Thursday.
(Reporting by Stanley White; Editing by Eric Meijer)