Processes for preparing a carbon black product having an organic group attached to the carbon black. In one process at least one diazonium salt reacts with a carbon black in the absence of an externally applied electric current sufficient to reduce the diazonium salt. In another process at least one diazonium salt reacts with a carbon black in a protic reaction medium. Carbon black products which may be prepared according to process of the invention are described as well as uses of such carbon black products in plastic compositions, rubber compositions, paper compositions, and textile compositions.