A simple and efficient method for selective cage B(3) multiple functionalization of o-carborane is described. Reaction of [3-N₂-o-C₂B₁₀H₁₁][BF₄] with various kinds of nucleophiles gave a very broad spectrum of cage B(3)-substituted o-carborane derivatives, 3-X-o-C₂B₁₀H₁₁ (X = OH, SCN, NH₂, NO₂, N₃, CF₃, PO(C₆H₅)₂, etc). This reaction may serve as another efficient [¹⁸F]-radiolabeling method of carborane clusters for positron emission tomography applications.