Deposits of commercial banks in the metropolitan Washington area rose by more than 12 per cent in the past year to a record $10.27 billion on Sept. 30, according to a Washington Post survey completed yesterday.

In the Maryland suburbs, deposits rose to $3.03 billion from $2.67 billion a year earlier. As reported in earlier, Virginia suburban deposits rose to $2.69 billion from $2.43 billion and District of Columbia bank deposits rose to $4.54 billion from $4.02 billion.

Although the pace of growth by D.C. banks has been somewhat higher in recent months than for institutions based in the suburbs, virtually all banks in the area have reported higher deposits. In general, regional growth of deposits in the past year has been at the most rapid rate since the 1960s.

The previous record high for area deposits was last June 30, when deposits were $10.14 billion.

Among Maryland banks showing above-average gains, American Bank of Silver Spring reported deposits of $179 million, a gain of $22 million from last year. Loan volume for the bank is up 36 per cent, and the bank earned $644,024 (84 cents a share) for the first nine months of the year compared with $202,209 (26 cents) a year earlier.

Big gains were posted by Suburban Trust Co. (up $103 million) and Citizens Bank & Trust Co. ($89 million, including deposits of Chevy Chase Bank & Trust, which was acquired by Citizens).