Cream butter; gradually add sugar, beating well. Combine flour and baking powder; gradually add to creamed mixture, mixing well. Stir in pecans. Cover, and chill 20 minutes or until dough is slightly firm.
Roll dough to 1/4-inch thickness between sheets of waxed paper. Remove top sheet of waxed paper. Cut dough into desired shapes with a cookie cutter; remove excess dough. Place ungreased cookie sheet on top of cookies; invert and remove waxed paper.
Bake at 300° for 25 minutes or until lightly browned. Remove immediately to wire rack to cool.