Polymeric micelles have a promising future in the treatment of cancer patients, and particularly as carriers in chemotherapy. The effectiveness of the micelles can be determined when their fate in vivo is known. Radiolabeling the micelles with diagnostic radionuclides allows for determination of their biodistribution and pharmacokinetics using nuclear imaging techniques. Besides imaging, therapeutic radionuclides can also possibly be applied to allow combination of radionuclide therapy and chemotherapy. In previous work, polymeric micelles were radiolabeled with ¹⁷⁷Lu, a therapeutic radionuclide. ¹⁷⁷Lu emits both β⁻ and γ radiation, β⁻ radiation can damage the tumor while the emitted γ radiation can be used for imaging purposes. For the clinical application of such micelles it is vital to determine their radiolabeling stability, i.e. the degree to which the radionuclides remain encapsulated in the micelles when exposed to serum or other conditions such as challenging with chelators. Size Exclusion Chromatography is a commonly used method to determine the radiolabeling stability but has proven to give inconsequent results when carried out in serum. In this research the radiolabeling stability of polymeric micelles was determined using Thin Layer Chromatography and DTPA as a competing chelator. Silica coated aluminum strips were loaded with sample, run using several different mobile phases, and analyzed through phosphor imaging and automated gamma counting. These experiments were then repeated under serum conditions. Experimental results of Thin Layer Chromatography with ¹⁷⁷Lu radiolabeled PCL-PEO micelles were then compared with Size Exclusion Chromatography results from earlier research. It was concluded that while the mobile phase used can influence the radiolabeling stability, Thin Layer Chromatography can provide an excellent method of efficiently determining radiolabeling stabilities of radiolabeled micelles under non-serum and serum conditions.