The present invention relates to humanized FcγRIIB antibodies, fragments, and variants thereof that bind human FcγRIIB with a greater affinity than said antibody binds FcγRIIA. The invention encompasses the use of the humanized antibodies of the invention for the treatment of any disease related to loss of balance of Fc receptor mediated signaling, such as cancer (preferably a B-cell malignancy, particularly, B-cell chronic lymphocytic leukemia or non-Hodgkin's lymphoma), autoimmune disease, inflammatory disease or IgE-mediated allergic disorder. The present invention also encompasses the use of a humanized FcγRIIB antibody or an antigen-binding fragment thereof, in combination with other cancer therapies. The invention provides methods of enhancing the therapeutic effect of therapeutic antibodies by administering the humanized antibodies of the invention to enhance the effector function of the therapeutic antibodies. The invention also provides methods of enhancing the efficacy of a vaccine composition by administering the humanized antibodies of the invention with a vaccine composition.