A radioimmunoconjugate comprised of the chimeric monoclonal antibody G250 conjugated with the positron emitter iodine I 124. The antibody moiety of iodine I 124 girentuximab may bind to renal cell carcinoma (RCC) cells that express the RCC-associated antigen G250, allowing detection of tumor-localized iodine I 124 with positron emission tomography (PET). G250 is a cell surface tumor-associated antigen (TAA) that is found in the majority of renal cell carcinomas.