WEST BERLIN -- West German Roman Catholics greeted the pope warmly during his recent visit, but just-published statistics suggest that the show of affection for the pope apparently has little to do with day-to-day religious practice.

Fewer Catholics are going to mass on Sunday, and a growing number are leaving the church, according to a report based on figures collected from the Catholic dioceses in the Federal Republic and West Berlin.

According to the figures, one Catholic in four attends mass on a given Sunday. In 1970, the figure was one in three.

Both baptisms and church marriages have dropped about 30 percent since 1970. With 113,000 marriages in 1985, the total reached the lowest point since the end of World War II.

There were marked differences among dioceses. West Berlin emerged as the least "churchy" place for West German Catholics, with one Catholic in eight attending mass on a given Sunday.

This year only one new priest will be ordained for the 278,000 Roman Catholics of West Berlin.

The number of people leaving the Catholic Church also reached a post-war high of 75,000 in 1985. Church officials don't expect the 1986 statistics to be any better.

The churches in West Germany are supported by contributions withheld by employers, the so- called church tax. A fairly accurate count of people leaving the church is available because those dropping church membership go to a city finance office to fill out declarations.

About 26.3 million Roman Catholics -- about a million more than the Protestants -- are among a total West German population of 61 million.

Protestant church attendance has always been low in West Germany. At the moment it amounts to single-digit percentages each week. In Berlin it is as low as 1 percent.