Gov. William Donald Schaefer has named Robert E. Cadigan to a judgeship on the Baltimore County Circuit Court.

Mr. Cadigan, 58, of Pinehurst is head of the general litigation section at the Baltimore firm Smith Somerville & Case. He succeeds Judge Leonard S. Jacobson, who took early retirement in February to work in the county's settlement court.

Mr. Cadigan has been a trial attorney, largely in the area of civil litigation, for 32 years.

Mr. Schaefer also named Durke G. Thompson of Potomac, 51, to the Montgomery County Circuit Court bench.

Mr. Thompson of Potomac, a partner in the Bethesda firm Pasternak, Thompson and Fidis, replaces Judge Irma S. Raker, whom the governor named to the Court of Appeals in January. Mr. Thompson has focused on personal injury law, professional disciplinary and ethical matters, and entertainment law.

Both new judges will serve until November 1996, when they may run to retain their seats.