Preheat oven to 350 degrees F (175 degrees C). Grease cookie sheets.
In a large bowl, cream together the butter and sugar until smooth. Blend in the egg and vanilla.
Combine the flour, cocoa, baking soda and salt; stir into the creamed mixture. Finally, mix in the chopped cherries and walnuts. Drop by rounded spoonfuls onto the prepared cookie sheets.
Bake for 8 to 10 minutes in the preheated oven. Allow cookies to cool on baking sheet for 5 minutes before removing to a wire rack to cool completely.