Preheat oven to 350 degrees. In a medium mixing bowl stir together flour, cocoa, baking soda, and salt. Set aside.
In a large mixing bowl with an electric mixer on medium speed cream butter and sugars until fluffy. Beat in eggs, one at a time, then vanilla. On low speed gradually add flour mixture and mix just until blended. Stir in chocolate chips and walnuts.
Drop dough by rounded tablespoonfuls two inches apart onto ungreased baking sheets. Bake for 12 to 14 minutes. Transfer cookies to cooling racks to cool.