A new congressional report indicated yesterday that the District of Columbia spent, in one recent year, much more money per capita than 18 other cities in the same size range, even when county and state expenditures to the other cities were considered.

The District spent more than twice as much per capita than 13 of the cities studied.

According to preliminary figures released yesterday by the Senate District Appropriations Subcommittee, the District spent $2,869 for each of its 733,801 residents in the 1974-75 fiscal year. Spending in the other cities ranged from a high of $2,004 in Boston, which has 618,275 residents, to a low of $890 in Indianapolis, with a population of 128,344.

The report was cited by Sen. Patrick J. Leahy (D-Vt.), who commissioned its preparation by the Congressional Research Service, as he opened a week of hearings into the city's $1.2 billion operating budget and $150 million capital budget for the 1978 fiscal year, which begins next Oct. 1.

Hearings by the House District Appropriations Subcommittee on the same budget were concluded Monday, although at least one more session must be scheduled to deal with proposed budget amendments.

As Mayor Walter F. Washington sat at the witness table at a Senate hearing that began at the uncommonly early hour of 8 a.m., Leahy questioned whether the city overspends its means. He urged that controls be tightened over recently disclosed high levels of welfare and Medicaid irregularities.

The report was cited by Sen. Patrick J. Leahy (D-Vt.) who commissioned its preparation by the Congressional Research Service, as he opened a week of hearings into the city's $1.2 billion operating budget and $150 million capital budget for the 1978 fiscal year, which begins next Oct. 1.

Hearings by the House District Appropriations Subcommittee on the same budget were concluded Monday, although at least one more session must be scheduled to deal with proposed budget amendments.

As Mayor Walter E. Washington sat at the witness table at a Senate hearing that began at the uncommonly early hour of 8 a.m., Leahy questioned whether the city overspends its means. He urged that controls be tightened over recently disclosed high levels of welfare and Medicaid irregularities.

It was the first session on the city's annual budget to be conducted by Leahy, a 37-year-old Georgetown University law school graduate and former prosecutor from Burlington, Vt., who assumed the subcommittee chairmanship in February.

To an audience composed chiefly of sleepy District bureaucrats who assembled two hours earlier than most congressional hearings begin. Leahy remarked, "I apologize to those who want to call the meeting earlier, but I need a couple of hours in the office . . . before committees start."

Sen. Charles McC. Mathias Jr. (H-Md.), who lives on a farm in Frederick County, replied, "It would be difficult for me to get in from the milking any sooner."

Leahy's reference to the new comparative report on municipal costs troubled D.C. budget director Comer S. Coppie, who had not seen it. Coppie disputed the validity of any tally that uses raw figures without accounting for community burdens, characteristics or priorities.

For example, Coppie said, Washington's daytime population - swelled by suburbanites and tourists - is 30 per cent greater than its resident population, the highest such influx of any big city in the nation. The comparable figure for New York City (which was not on Leahy's basic comparison list) is 8 per cent, Coppie said.

A Leahy aide said the figures in the report will be refined further before the document is issued in final form. The report is based largely on U.S. Census data and covers all U.S. cities in the population range between 500,000 and 1 million.

With the report, Leahy said he hoped to clarify one area of District finances that often causes confusion - how to compare the expenditures of the District, which performs the services of a city, a county and a state, with expenditures of other cities whose taxpayers contribute funds to and receive services from counties states and independent districts (such as school districts in which they are located.

The report did not attempt to break down the money spent on various forms of public service, such as education, health or welfare. Nor did it trace the sources of the money, which include taxes, fees, federal and state grants and utility fees.