This paper describes the biodistribution of a radio-iodinated analog of fluorodeoxyglucose (FDG). 123I-2-fluoro-2-iodo-mannose (FIM) was investigated as a potential single photon emission tomography (SPECT) imaging agent. We also compare the results with the observed distribution of the classical PET agent 18F-FDG and newly developed 18F-difluorodeoxyglucose (DFDG). Following radioiodination, the final product was stable in-vitro for 24 hrs. Mice showed a rapid blood clearance and deiodination of the 123I-FIM reflected by high stomach and thyroid uptake. Comparison with 18F-FDG and 18F-DFDG revealed a large discrepancy between the 18F labeled sugars and the 123I-FIM biological distribution. The iodinated product was not found to be a metabolic marker for in-vivo studies.