Cynthia Voigt's "Dicey's Song" has won the 1983 Newbery Medal for the most distinguished children's book of the year. And "Shadow," illustrated by Marcia Brown, has been awarded the Caldecott Medal as the year's best picture book for children.

The winners were chosen yesterday by the Association for Library Service to Children. The 4,000-member group--part of the American Library Association, which is meeting in San Antonio--awards the prizes annually "to call attention to and stimulate distinguished writing and illustration in books for children."

"Dicey's Song" (Atheneum) is the sequel to Annapolis author Voigt's first novel, "The Homecoming." The new book, intended for ages 12 and up, depicts a group of children who are sent to live with their grandmother when their mother is confined to a faraway mental hospital. The title reflects the anxieties of Dicey, the central character, about whether they will ever have a permanent home.

Brown, who previously won Caldecott medals in 1955 and 1962, illustrated and translated "Shadow" (Scribners) from Blaise Cendrars' prose-poem about the ritual significance and mystery of the shadow figure in African tribal life.

In addition to the medalists, the ALSC's two award panels also name a number of "honor books" each year. This year's Newbery honor books are "The Blue Sword," by Robin McKinley (Greenwillow); "Doctor De Soto," written and illustrated by William Steig (Farrar Straus & Giroux); "Graven Images," by Paul Fleischman, illustrated by Andrew Glass (Harper & Row); "Homesick: My Own Story," by Jean Fritz, illustrated by Margot Tomes (Putnam); and "Sweet Whispers, Brother Rush," by Virginia Hamilton (Philomel Books).

Named as Caldecott honor books were "A Chair for My Mother," illustrated and written by Vera B. Williams (Greenwillow), and "When I Was Young in the Mountains," by Cynthia Rylant, illustrated by Diane Goode (Dutton).

The Newbery Medal, awarded annually since 1922 to "the most distinguished contribution to American literature for children," is named for John Newbery, an 18th-century publisher of children's books and friend of Samuel Johnson. The Caldecott Medal for "the year's most distinguished American picture book for children" was first given in 1938. It is named in honor of 19th-century British illustrator Randolph Caldecott. No money accompanies the awards, but they are regarded as virtual guarantees of wide and enduring sales. Of the 106 Newbery and Caldecott books named in the awards' history, only seven are currently out of print.

The winners will receive their medals June 28 at the ALA's annual conference in Los Angeles